Who devised the periodic table and when?
Dimitri Mendeleev, in the mid 19th century (even predicted new elements - left space for them).
How are the elements in the periodic table arranged?
In order of increasing atomic number.
Atomic number?
Number of protons (and electrons, e.g. 7 means 7 protons and 7 electrons).
Mass number?
Number of protons + neutrons.
Why is the table arranged in periods?
Mendeleev realised the elements display a pattern of chemical properties at regular intervals, so every time the pattern repeated he formed a new row which is called a period. (Which is why elements in groups have similar chemical properties).
Why do elements in each group happen to have similar chemical properties?
Because they have the same number of electrons in their outermost shell which is largely what determines their reactivity.
What type of ions do metals form?
Positive.
What type of ions do non-metals form?
Don’t form ions (e.g. carbon) or form negative ions.
Why do metals tend to become more reactive near the bottom of the group?
Because the outermost shell will get further away from the positive nucleus (because the atoms will have more shells making them larger) and weakens the electrostatic attraction between the outermost electrons and the positive nucleus and less energy is required to overcome the electrostatic attraction so the electron can be lost more easily during reactions -> more reactive.
Why do metals tend to form positive ions?
Because they have less electrons in their outermost shell so its easier to loose the few rather than gain lots to become stable.
Physical properties of metals (6)?
1) Have metallic bonding (very strong, responsible for metals physical properties).
2)Malleable (can be bent/ hammered into shape).
3) Good conductors of heat and electricity (used in electric wires).
4) Have high melting and boiling points (why?)
5) Shiny.
6) Sonorous (ringing sound when hit).
Physical properties of non-metals (5)?
1) Dull in colour.
2) lower densities (weigh less for a given volume)
3) brittle (can break easily)
4) poor conductors of heat and electricity.
5) generally low melting and boiling points (many are gaseous at room temp).
Transition metal properties(3)?
1) Typical metal properties.
2) Good catalysts.
3) Can form more than one ion (often coloured aqueous solutions).
What’s a catalyst?
Substances which increase the rate of a chemical reaction without being used up themselves.
What group are alkali metals?
Group 1.
Name all alkali metals in order of least to most reactive.
Lithium, sodium, potassium, rubidium, caesium and francium.
Physical properties of alkali metals (3)?
Unlike other metals:
1) quite soft.
2) low density.
3) low melting point.
Trends going down group 1?
Elements become more reactive (caesium can even ignite spontaneously at room temp) and melting and boiling points decrease.
Why can alkali metals easily form ionic compounds?
Because they can loose their outer electrons more easily to form ionic compounds with non-metals.
Give the general equation for when alkali metals react with water.
Alkali metal + water -> metal hydroxide + hydrogen (gas)
They react very vigorously with water.
How do alkali metals react with chlorine?
Very vigorously (more vigorous as you go down the group like with water) when heated in chlorine gas to form white metal chloride salts (e.g. sodium chloride).
How do alkali metas react with oxygen? What does the reaction produce (give named examples)
The form metal oxides, which the type depends on the metal. (Lithium oxide, sodium oxide/ sodium peroxide, potassium peroxide/ potassium superoxide KO2).
Experiment; reacting alkali metals and observations:
Chemical property of alkali metals?
More reactive than other meals. React vigorously with water, oxygen and group 7 elements such as chlorine.
