What are noble gases?
- noble gases are monatomic
> exists as individual atoms
> stable and unreactive - do not usually react with other elements to form compounds
- elements of group 0: Helium (He)
, Neon (Ne)… etc
How do atoms achieve the electronic configuration of noble gases?
- atoms of elements (except for noble gases), do not have fully filled outer shells
- they are reactive
> undergo reactions to achieve stable electronic configuration of a noble gas
1. Losing outer electrons
2. Gaining outer electrons
3. Sharing outer electrons
READ AND UNDERSTAND!
- atom becomes an ion if it loses or gains electrons
> number of protons and electrons are different
> ions carry a positive charge or a negative charge
- metals form positively charged ions ( cations) and non-metals form negatively charged ions (anions)
The chapter you’re learning today is going to save someone’s life tomorrow. So pay attention.
What is 1. duplet electronic configuration and
2. octet electronic configuration?
1.has two outer electrons
>helium
2. Atoms of noble gases have 8 outer electrons
How are positive ions formed?
- cations formed when atoms lose electrons
- atoms of metals generally only have a few outer electrons
> tend to lose electrons to form cations - when an atom loses electrons, it has more protons than electrons
> positive ion - the charge on a cation corresponds to the number of electrons the atom loses
How are negative ions formed?
- anions formed when atoms gain electrons
> generally, non-metals have more than 4 outer electrons
> tend to gain electrons to form anions
>more electrons than protons
>anion is formed
Draw a dot diagram of
1. Chlorine atom > _______ ion
2. Oxygen atom > _______ ion
- Chloride ion
- Oxygen ion
Look at page 93 of textbook
What are ionic bonds?
- are the strong electrostatic forces of attraction between positive and negative ions
Draw a dot-and-cross diagram of the formation of sodium chloride.
Things to remember when drawing:
Page 97
Draw a dot-and-cross diagram of the formation of magnesium chloride.
Things to remember when drawing:
Page 97
Draw a dot-and-cross diagram of
1. Sodium atom > sodium ion
2. Magnesium atom > magnesium ion
Refer to page 92 of tb :)
what are polyatomic ions and what are some examples of it?
- ions composed of two or more covalently bonded atoms
eg: ammonium ion (NH₄⁺), carbonate ion (CO3 2-), sulfate ion ( SO₄²-)
pg 95 of tb :)
turn to page 97 & 98 on general rules for chemical formulae of ionic compounds
yes
how do we deduce the chemical formula of an ionic compound?
- all the positive charges must be equal to the negative charges in an ionic compound
> construct the formula of an ionic compound by balancing the charges on the positive ions with those on the negative ions
deduce the chemical formula of :
(i) calcium chloride
(ii) aluminium oxide
(iii) magnesium oxide
(iv) copper (II) hydroxide
(v) ammonium sulfate
(vi) calcium carbonate
(i) calcium chloride: CaCl2
(ii) aluminium oxide: Al₂O₃
(iii) magnesium oxide: MgO
(iv) copper (II) hydroxide: Cu(OH)₂
(v) ammonium sulfate: (NH₄)₂SO₄
(vi) calcium carbonate: CaCO3
page 99 of tb :)
what is the formula of these cations?
1. ammonium
2. copper (II)
3. iron (III)
4. chromium (III)
- NH₄⁺
- Cu 2+ (2+ on top)
- Fe 3+ (3+ on top)
- Cr 3+ (3+ on top)
what is a giant ionic lattice structure?
- it is a three dimensional network of ions
- ions packed together in a regular and repeating pattern
- giant lattice structure held together tightly together and ions held in fixed positions
> cuz the oppositely charged ions attract one another strongly
pg101
how can we deduce the formula of sodium chloride from its lattice structure?
- To deduce the formula
> can determine the ratio of sodium ions to chloride ions in a formula unit
in lattice structure of sodium chloride: - each Na+ ion is surrounded by six Cl- ions
-each Cl- ion is surrounded by six Na+- ions - the overall ration of sodium ions to chloride ions is 1:1
- formula of sodium chloride: NaCl
What are the physical properties of ionic compounds?
- most ionic compounds have high melting and boiling points
- in ionic compounds, the forces of attraction between oppositely charged ions > strong
- large amount of heat is needed to overcome the strong forces of attraction to melt the ionic compound
- due to high b.p and m.p
> most ionic compounds are solids at room temperature and pressure
> ionic compounds are non volatile - are usually soluble in water and insoluble in solvents
> usually soluble in water BUT ionic compounds like
> silver chloride and barium sulfate is insoluble in water
- insoluble in organic solvents such as:
>oil, petrol, turpentine - conduct electricity when molten or in aqueous solution ( dissolved in water)
why are most ionic compounds soluble in water and insoluble in solvents?
- water molecules are attracted to ions
> weakens the electrostatic forces between the ions
> ions pulled from the lattice structure compound dissolves to form an aqueous solution - in organic solvents, no water present
> insoluble in them and remain tightly held in the lattice structure
why do ionic compounds conduct electricity when molten or dissolved in water? but not in solids?
- there must be free moving ions or electrons in order to conduct electricity
- when it is molten or dissolved in water to form an aqueous solution
> cations and anions are free to move and are able to conduct electricity - however, there are no free moving ions to conduct electricity in the solid state since the ions are held in place in the lattice structure
what are the formula of these anions:
1. hydrogen carbonate
2. hydroxide
3. nitrate
4. carbonate
5. sulfate
6. phosphate
- HCO3 - ( - on top)
- OH - ( - on top)
- NO3 - ( - on top)
- CO3 2- ( 2- on top)
- SO4 2- ( 2- on top)
- PO4 3- ( 3- on top)
what do chemical formulas show?
the number of atoms and the type of elements in a compound
what are the chemical formulas for the following acids:
1. Hydrochloric acid
2. nitric acid
3. Phosphoric acid
4. Sulfuric acid
- HCl
- HNO3
- H3PO4
- H2SO4
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chapter 1: kinetic particle theory14
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chapter 2: measurement and experimental techniques11
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chapter 3: separation and purification25
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chapter 4: elements, mixtures and compounds12
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chapter 5: atomic structure9
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chapter 6: ionic bonding24
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chapter 7: covalent and metallic bonding23
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chapter 16: periodic table16
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chapter 13: oxidation and reduction6
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chapter 14: metals18
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chapter 11: acids and bases16
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chapter 12: salts0
