1
Q
What are the properties of metals?
A
- Most of the known elements are metals. *Most metals are
solids at room temperature. - Metals have a range of properties, particularly in colour,
melting point boiling point and reactivity with oxygen,
water and acids. - Most metals have the following properties; They are
- Shiny
- Malleable\ductile
- Good thermal conductors
- Good electrical conductors
- Higher density
2
Q
What are the properties of non-metals?
A
- Non-metals are liquids and gases at room temperature although
there are some exceptions - Most non-metals have the following properties; They are
- Poor thermal conductors
- Poor electrical conductors
- When in solid state they tend to be dull in colour and brittle. They
have low melting and boiling points - They do not react with water and are the same or lower in density
3
Q
who created the periodic table?
A
In 1869, Russian chemist Dmitri Mendeleev developed the modern periodic table of elements.
He arranged the elements based on their properties into a table of repeating patterns.
4
Q
define brittle
A
if a force is applied a substance breaks into smaller pieces
5
Q
define malleable
A
when matter can be hammered into a shape or flattened without shattering
6
Q
define ductile
A
can be drawn out into a wire
7
Q
define thermal conductivity
A
The ability of a material to conduct heat
8
Q
define electrical conductivity
A
The ability of a material to conduct electricity
9
Q
define insulator
A
A material that does not allow electricity or heat to pass through it easily
10
Q
define density
A
a measure of the amount of matter in a given space – how tightly the particles are packed in together
11
Q
define lustre
A
Shine that is reflected from a surface
12
Q
what are metalloids?
A
Metalloid elements exhibit properties of both metals and nonmetals.
They are generally metal in appearance but are non-metallic in their chemical behaviour.
13
Q
what makes up the periodic table?
A
Metals and non metals make up all of the periodic table and they are arranged in order of their atomic number. The periodic table can be separated into two large sections. - the metals and non-metals, these are separated by the stairs of metalloids from Boron to Astatine.
14
Q
how many periods and groups are there?
A
18 groups and 7 rows
15
Q
what are periods?
A
Periods = rows.
Atomic number increases across each period.
16
Q
what are groups?
A
Groups = columns.
Elements in the same group have similar properties.
17
Q
where are transition metals?
A
Transition metals are the block of the periodic table.
18
Q
what is group 1?
A
Alkali Metals
19
Q
properties of Alkali Metals?
A
- Highly reactive (1 valence electron), especially with oxygen and water
- Never found in nature as an element, only as a compound
- The Group 1 Elements are mostly soft and silver-coloured metals, but tarnish quickly
- They have both low densities and low melting and boiling
points. - Since they are metals, they are good conductors of heat, malleable, and ductile
- become more reactive as you go down the group
20
Q
what is group 2?
A
Alkaline Earth Metals
21
Q
properties of Alkaline Earth Metals?
A
- Reactive, but not as much as the alkali metals (2 valence electrons)
- Never found in nature as an element, only as a compound
- Low melting point
- Relatively soft
- All of the elements in Group II are metals, so they all have the properties of metals including lustre, malleability, ductility and conductivity.
- Calcium, strontium, and barium react vigorously at 25 degrees Celsius
- The metals of group 2 are harder and denser than sodium and potassium, and have higher
melting points but still low - low density
- become more reactive as you go down the group
22
Q
what is group 17?
A
Halogens
23
Q
properties of halogens?
A
- Non-metals
- Very reactive (7 valence electrons)
- Become less reactive as you move down the group (opposite of group 1 and 2)
- Readily combine with metals to form salts
- highly coloured
- low melting and boiling points
- tend to be found as a diatomic molecule
24
Q
what is group 18?
A
Noble gases
25
properties of Noble gases?
- Colourless, odourless gases at room temperature
- Do not react with other elements, are inert (full valence shell)
26
what is the atomic number?
- number of protons in the nucleus
- also the number of electrons in a neutral atom
27
what is the atomic mass?
- the number of protons and neutrons in the nucleus of an atom
28
how do electrons fill the shells?
Electrons fill the electron shells in order, starting with the innermost shell closest to the nucleus.
29
what is the electron configuration?
max number of 2,8,18,32
However as the energy difference between shell 3 and 4 is too close after 8 electrons they fill shell 4.
For the elements 1-20, the maximum number of electrons for each shell is 2,8,8,2.
30
what is the valence shell?
The valence shell is the outermost level (shell) and valence electrons participate in chemical reactions to make the atom stable.
31
groups and rows in relation to valence electrons and shells
Groups have the same number of valence electrons.
Rows contain the same number of shells.
32
how do electrons exist?
Electrons like to exist in pairs, and should be drawn that way. However they always fill the four points around the atom first (except for the first shell).
33
why are noble gases non-reactive?
they have a full valence shell
34
describe the reactivity of metals
- Elements ‘want’ to be like the noble gases – stable, with 8 valence electrons.
- Metals react when they lose their valence electrons in order to achieve a full valence shell.
- Metals with more electron shells lose their valence electrons more easily as the attraction of the nucleus is reduced.
35
describe the reactivity of non metals
- Nonmetals react when they gain valence electrons in order to achieve a full valence shell.
- Nonmetals with more valence electrons are more reactive as it is easier for them to gain a full outer shell.
- Nonmetals with fewer electron shells gain a full outer shell more easily as the attraction of the nucleus is increased.
36
what are pure elements found as?
Pure elements are found as atoms, molecules or lattices
37
what are single atoms?
Eg: helium, neon and other noble gases as they are unreactive
- Single atoms bouncing around
- Only gases
38
what are molecules?
Eg: hydrogen H2and oxygen O2
- Small groups of atoms bonded together
- Can be solid, liquid or gas.
- Typically non-metals
39
what are lattices?
Eg: Gold and iron
- A lattice is a atoms packed together into a large regular arrangement
- Metals, alloys (mixtures of metals), ionic compounds (metals mixed with non-metals) and some covalent compounds (e.g glass) are arranged in lattices.
- Some ELEMENTS like metals and non-metals including sulfur and carbon are found in the form of lattices.
40
what does a chemical formula tell you?
A chemical formula will tell you what atoms are present and the amount of each type of atom found in the molecule or lattice
41
what do symbols, subscripts, brackets and coefficients do in chemical equations?
Symbols - Each capital letter means that there is a new element
Subscripts - A number that comes after a symbol and below the subscript only affects the element it comes after.
Brackets - A subscript outside a bracket affects all the elements inside the bracket (ie. Multiply!)
Coefficients - A “full size” number in front of a chemical formula. Multiplies everything in the formula.
42
what holds electrons and molecules together?
The electric forces between oppositely charged electrons and protons hold atoms and molecules together.
43
what is a chemical bond?
A chemical bond is the force that holds atoms together in a compound. When atoms gain, lose, or share electrons, an attraction forms between the atoms, pulling them together to form a compound
44
what are metallic bonds?
The bonds that form between metal atoms are called metallic bonds. The metals might be pure or a mixture of metals called an alloy eg: brass or bronze
45
what are covalent bonds?
Bonds that form between non-metal atoms are called covalent bonds. They occur by two or more atoms of the same or different types sharing electrons.
46
what are ionic bonds?
Bonds that form between metals and non-metal atoms are called ionic bonds. The bonds form because electrons get passed from metal atoms to non-metal atoms forming positive and negative ions which are then attracted together.
47
how do you name ionic substances?
- Name the metal then the non-metal
- The metal keeps its name
- The non-metal has the suffix changed to “ide”
- DO NOT USE PREFIXES
48
how do you name covalent substances?
- Name from left to right on the periodic table
- First element keeps its name
- The second element has its name changed to-ide
- The first element gets the prefix if it has a subscript.
- The second always gets a prefix
49
what are the prefixes?
1 - mono
2 - di
3 - tri
4 - tetra
5 - penta
6 - hexa
7 - hepta
8 - octa
9 - nono
10 - deca
50
what is an ion?
An ion is an atom or molecule that has an unequal number of protons and electrons, giving it an overall positive or negative charge. A charged particle.
51
what are cations?
Elements that lose electrons become positively charged ions (more protons than electrons).
Positive ions are called cations. Generally metals.
52
what are anions?
Elements that gain electrons become negatively charged ions (more electrons than protons).
Negative ions are called anions. Non-metals only.
53
what is an ionic bond?
- An ionic bond is the electrostatic attraction between a positive ion (cation) and a negatively charged ion (anion). The electron that is given up by the metal atom can be taken up by the non-metal atom.
- Ionic bonding occurs between metal cations and non-metal anions to make ionic compounds.
- It involves a transfer of valence electrons from one element to the other.
- The oppositely charged ions are strongly attracted to each other and arrange themselves in a 3D pattern – a lattice.
54
Ammonium
NH4 +
55
Hydrogen carbonate
HCO3 -
56
Hydroxide
OH -
57
Nitrate
NO3 -
58
Carbonate
CO3 2-
59
Sulphate
SO4 2-
60
Phosphate
PH4 3-
61
Iron
Fe(II) or (III) = 2+ or 3+
62
Copper
Cu(II) or (III) = 2+ or 3+
63
ionic compound properties
* They are made up of positive and negative ions
* They are usually solids at room temperature
* They normally have very high melting points and boiling points because the electrostatic
force of attraction between the ion is very strong
* They form crystals
* They usually dissolve in water to form aqueous solutions
* The aqueous solutions normally conduct electricity because the ions are free to move
* The solids do not conduct electricity – they are insulators
* They are hard and brittle
64
what is electrovalency?
- Electrovalency is the number of charges on the ion.
- some transition metals have multiple electrovalencies
65
what are polyatomic ions?
* A small cluster of non-metal atoms joined together with an overall charge is called a polyatomic ion. The non-metal atoms are joined by covalent bonds but the cluster will have gained (or lost in the case of ammonium (NH4+) one or more extra electrons.
*The cluster will be written in a bracket in the formula if there is more than
1 polyatomic ion in the formula.
- a polyatomic ion is formed when a neutral molecule gains or loses electrons.
66
how to name ionic compounds?
The cation (metal) is always named first.
The anion (non-metal) is listed second:
If it is an element, the name now ends in ‘ide’
e.g. NaCl = sodium chloride.
If it is polyatomic it keeps its name.
e.g CaCO₃ = calcium carbonate
67
what is a chemical reaction?
In a chemical reaction, chemical bonds within substances are broken, atoms are rearranged and new bonds are formed to create new compounds/molecules.
68
how are chemical equations written?
Chemical equations are written representation of chemical reactions:
Reactants ---> Products
States of matter are included with the formulae in a chemical equation, but not included in a word equation.
69
how can you tell is a chemical reaction has occurred?
You can tell a chemical reaction has occurred if there is a colour change, a temperature change, light, sound, bubbles or a precipitate is formed.
70
what is the law of conservation of mass?
The Law of Conservation of Mass states that in a chemical reaction atoms cannot be created or destroyed.
The mass of the reactants should be equal to the mass of the products .
The number of atoms of each element in the reactants must equal that of the products. The only thing that is different is how the atoms are arranged.
71
how can you balance chemical equations?
You can only add coefficients to balance equations.
72
what are the 4 types of reactions?
Combination A + B = AB
Decomposition AB = A + B
Single Replacement AB + C = A + BC
Double Replacement AB + CD = AD + BC
73
what happens in chemical reactions with energy?
- Energy may be exchanged between the chemicals in the reaction and the surrounding environment.
- During a reaction, energy may be released or absorbed.
74
what are exothermic reactions?
- Reactions that release heat energy and warm the surrounding environment.
- Chemical energy stored in the molecules of the reactants is released as heat.
- Reactants have a high amount of stored chemical energy and products have low amounts
75
what happens in a exothermic reaction?
1. As heat is given out in the surroundings in this reaction, it causes a rise in temperature.
2. In the exothermic reaction, energy is released because the total energy of the product is less than the total energy of the reactants.
3. That means it takes less energy to break bonds in the reactants than is released when new bonds form in the product
If the energy released from making bonds is greater than the energy needed to break bonds, the reaction is EXOTHERMIC.
76
what is an endothermic reaction?
- Reactions that absorb heat and cool the surrounding environment.
- Heat energy is absorbed and converted to chemical energy stored in molecules.
- Reactants have a low amount of stored chemical energy and products have high amounts
77
what happens in an endothermic reaction?
1. This reaction causes a fall in temperature.
2. Exothermic reactions cannot occur spontaneously.
3. For this reaction to occur, external energy must be supplied.
If you need lots of energy to break bonds and not much is released from making bonds, the reaction is ENDOTHERMIC.
When the reaction happens, the bonds between some atoms are broken apart. Other atoms are joined together with new bonds.
78
whats an energy profile diagram?
The diagram shows the relative amount of energy held in the reactants in comparison to the products. It allows you to determine the amount of energy taken in or given out overall (provided the diagram has a scale on the y axis) Finally it shows the activation energy – the energy needed to initiate the reaction by breaking apart the reactants.
79
what are combustion reactions?
- Combustion reactions are exothermic reactions that involve the burning of a fuel by reacting it with oxygen.
- When a combustion reaction occurs extremely rapidly it may cause an explosion.
- In an explosion the reactants release their chemical energy over a very short period of time.
80
what is a precipitate?
- A precipitate is a solid formed from reactions in solutions
- Precipitates form from the mixing of two or more aqueous solutions containing ions that can react and form insoluble compounds.
81
what are the characteristics of a precipitate?
solid state, often appearing as fine particles or crystals suspended in a liquid
82
what happens in a precipitation reaction?
* When mixed the metal ions swap to potentially form new products (this is a double replacement reaction)
* If one of the products has low solubility it will become visible as a precipitate (small particles of floating solid that look cloudy)
83
what can/cannot water dissolve?
Water cannot dissolve non-polar substances like oils
Water can dissolve:
- ionic compounds or salts or eg: NaCl.
- some covalent molecules like alcohols and - sugars
- Acids
84
what is solubility?
Solubility is the extent to which a solute (what gets dissolved) can dissolve in a solvent.(what does the dissolving)
85
what does supersaturated mean?
Supersaturated is an increase of the concentration of (a solution) beyond saturation point. Heated up and then cooled down
86
what is the solubility influenced by?
the temperature
87
what is a saturated solution?
The maximum amount of solute that can dissolve in a solution at a particular temperature gives a saturated solution.
88
whats an unsaturated solution?
a solution that has less than the amount of solute that can dissolve in a solution at a particular temperature.
89
what happens when ionic compounds are added to water?
they often dissolve and the cations and anions are free to move about
90
whats the process of diassociation?
Ionic compounds dissolve in water and separate into their constituent ions.
91
what is a solubility curve?
* A solubility curve is produced when the solubility of a substance (measured in g/100g) is plotted against the temperature.
* Solubility curves accurately represent the amount of solute in a solution at a particular temperature.
* From a solubility curve you can predict the amount of solute present in a solution at a particular temperature, or the amount that will dissolve, or the amount that will not dissolve when a given amount is added to a known amount of solution.
92
what are acids?
Acids are substances that have the following common properties:
- They have a sour taste
- They react with metals
- They can be corrosive
- They are solutions of a compound dissolved in water
Acids: Hcl, HNO3, Vinegar
93
what are bases?
Bases are substances that have the following common properties:
- They can be solid or liquid.
- Some solid bases can be dissolved in water. A base that is soluble in water is called an alkali.
- They have a soapy, slippery feel.
- They have a bitter taste.
- They are corrosive. Because strong bases burn the skin, they are also described as caustic.
Bases: Soap, NaOH
94
what are neutral substances?
A neutral substance is any substance that is neither an acid nor a base. In fact, when acids and bases mix, they react to form neutral substances.
Neutral substances have the following properties:
- They are not corrosive – they tend to be harmless to the touch.
- They may have a sweet or salty taste, or no taste.
95
what is the pH scale?
All solutions (dissolved in water) will be able to be measured on the pH scale.
0-(Acid)-7(Neutral)-14 (Base)
96
what are the reactions for acids and bases?
1) Acid + metal ---> salt + H2(g)
2) Acid + base ---> salt + H2O(l)
3) Acid + metal carbonate ---> salt + CO2(g) + H2O(l)
97
what are some acids?
hydrochloric acid (HCl), nitric acid (HNO3), Sulfuric acid (H2SO4), acetic acid (CH3COOH)
98
what are some bases?
sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonia (NH3), calcium hydroxide (CaOH) and calcium carbonate (CaCO3)
99
what are indicators?
Indicators are substances that change colour depending on whether they are in an acid or base.
100
what is the universal indicator of acids and bases?
Universal indicator changes colour depending on the specific pH:
Red = Very acidic
Green = Neutral
Violet = Very basic
101
what is collision theory?
* Collision theory says that reactant particles must collide with enough energy and with the correct orientation for a reaction to proceed.
* The collision energy is required because bonds in the reactant molecules must be broken before new bonds (in the products) can be formed. This is called the activation energy.
* Reactants must also collide with the correct orientation.
102
what happens if the orientation of particles aren't correct?
* If the orientation isn’t correct or there isn’t enough energy available to the reactants the molecules will just bounce off each other.
103
what is the rate of reaction?
the time taken for a reaction to occur, some factors can increase the rate of a reaction but the total amount of product formed is determined by how much reactant is available at a given temperature
104
what can reaction rates be influenced by?
* Temperature
* Concentration of solutions and gases
* Stirring and increasing the surface area of reactants
* Addition of catalysts
105
Why does temperature increase rate?
All particles have a certain amount of kinetic energy (energy of movement).
If you increase the temperature, you increase the kinetic energy of the particles. This means they are travelling faster, and more collisions are likely.
Also, when they collide there is a greater chance there will be enough energy to break the bonds and form products.
106
Why does concentration increase rate?
When you increase the amount of reactant there will be a greater chance that collisions occur and if more collisions occur there is a greater chance that they will have the right conditions to make a successful collision forming products. (also increasing pressure has the same effect on gases)
107
Why does increasing surface area increase rate?
* When you react a solid with a liquid or gas the only place where the right combination of atoms to produce the product molecules is possible is at the interface between the solid and the other medium.
* If you smash up the solid you can increase the surface area where the reaction can occur.
108
Why does agitation increase rate?
Similarly, if you want to increase the rate that a solid dissolves in a liquid (sugar in tea) you stir it around. This helps to bring reactants together because it moves away the product that has formed. Also helpful when a solid is heavy and tends to settle in the bottom of a reaction vessel.
109
what is a catalyst?
A catalyst is a substance that is added to a reaction vessel, which speeds up the rate of a reaction BUT it isn’t a reactant and therefore it isn’t used up in the reaction. A catalyst is written over the arrow in a chemical equation.
110
Why do catalysts increase rate?
* Catalysts work by binding to a reactant and forming an intermediate complex which is easier to break down, either:
– because it takes less energy (the activation energy is lower), or
– because it changes the physical orientation of the molecules making it easier for collisions to have the correct orientation.
111
what are the solubility rules?
Soluble salt:
- group 1 elements
- ammonium ion
- nitrate ion
- Cl-,Br-, I-
- Sulphate
Insoluble Salts:
- silver
- sulfide of transition metals
- carbonates
- chromates
- phosphates
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