Elements are classified as metals or non-metals based on their electrical conductivity and the acid-base properties of their oxides. Metals are good conductors, form positive ions, and have basic oxides. Non-metals are generally poor conductors and form negative ions or covalent compounds, with acidic or neutral oxides. Elements in the same group have similar properties because they have the same number of electrons in their outer shell. The noble gases have full outer electron shells, making them very unreactive. Group 1 elements react vigorously with water to produce hydroxides and hydrogen gas, with reactivity increasing down the group as the outer electron is farther from the nucleus. The halogens exist in different physical

1. 2.3 - explain the classification of elements as metals or non-metals on the basis of their electrical
conductivity and the acid-base character of their oxides.
1. Metals
2. Tend to be solids with high melting and boiling points, and with relatively high densities. (A few
exceptions)
3. Are shiny when they are polished (metallic lustre), and tend to be easily workable
4. Are good conductors of electricity and heat
5. Form positive ions in their compounds
6. Have oxides which tend to be basic; reacting with acids to give a salt and water.
Non-Metals
1. Tend to have low melting and boiling points (exceptions –carbon and silicon)
2. Tend to be brittle as solids and, even if they are crystalline, they don’t have the same sort of shine as
metals
3. Don’t usually conduct electricity (exceptions –carbon and silicon)
4. Are poor conductors of heat
5. Tend to form negative ions and covalent compounds
6. Have oxides which are acidic or neutral
2.4 - understand why elements in the same group of the Periodic Table have similar chemical properties
 (The atomic number counts the number of protons in the atoms of the element, which is equal to the
number of electrons in the neutral atom).
 Elements in the same Group have the same number of electrons in their outer energy levels (shells).
 That governs how they react, and means that elements in the same Group will have similar chemical
properties.
2.5 - understand that the noble gases (Group 0) are a family of inert gases and explain their lack of reactivity
in terms of their electronic configurations.
 The noble gases are all colourless gas.
 All the gases are monatomic. This means their molecules consist of single atoms.
 Their densities and boiling points illustrate typical patterns (trends) in physical properties as you go
down a Group in the periodic table.
1. The density increases as the atoms get heavier.
2. The boiling points also increase as you go down the Group.
3. This is because the attractions between one molecule and its neighbours get stronger as the atoms
get bigger.
4. More energy is needed to break the stronger attractions.
5. In helium, these intermolecular attractions are very, very weak.
6. Very little energy is needed to break these attractions, and so helium’s boiling point is very low.

2.  Group 0 is called the Noble Gases.
 This group of gases used to be called the inert gases.
 Inert means chemically unreactive.
 These elements do not readily form compounds with other elements.
 Helium, although sometimes not placed in group 8, is inert and is therefore a noble gas.
 The reason for the lack of reactivity is the number of electrons in the outer shell of each atom.
 Helium and neon atoms have full outer shells, and the rest have eight electrons in their outer shells.
 None of the atoms either gains of loses electrons easily.
The noble gases don’t form stable ions, and so don’t produce ionic compounds. They are reluctant to form
covalent bonds because, in most cases, it costs too much energy to rearrange the full energy levels to produce
the single electrons that an atom needs if it is to form simple covalent bonds by sharing electrons. That means
that these gases are generally unreactive.
Group 1 elements – lithium, sodium and potassium
2.6 - describe the reactions of these elements with water and understand that the reactions provide a basis
for their recognition as a family of elements.
 They are very reactive metals and are stored under oil to prevent them from reacting with oxygen or
water.
Physical properties
1. They are good conductors of electricity and of heat
2. They are soft and can easily be cut with a knife
3. They have low melting and boiling points compared with more typical metals such as iron and copper
4. They have low densities ( all three will float in water)
Chemical properties
1. They have shiny surfaces when freshly cut with a knife, but the surface quickly becomes dull
(tarnishes) as the metal reacts with oxygen in the air
2. They burn in air or oxygen to form white, solid oxides. The equation for this is :
2M + O2  M2O (where M = Li, Na or K)
3. They react vigorously with water to give an alkaline solution of the metal hydroxide as well as
hydrogen gas. The equation for this is:
2M + 2H2O  2MOH +H2 (where M = Li, Na or K)

3. Observations made when Li, Na or K are added to water:
Metal Observations
Lithium  Moves around the surface of the water
 Hissing sound
 Bubbles of gas
 Gets smaller and smaller; eventually
disappears
Sodium  Moves around the surface of the water
 Hissing sound
 Bubbles of gas
 Melts into a shiny ball
 Gets smaller and smaller; eventually
disappears
Potassium  Moves around the surface of the water
 Hissing sound
 Bubbles of gas
 Melts into a shiny ball
 Burn with a lilac-coloured flame
 Gets smaller and smaller; eventually
disappears
 The order of reactivity of the three metals is:
1. Potassium
2. Sodium
3. Lithium
 That is, the metals become more reactive with increasing atomic number.
2.7 - describe the relative reactivities of the elements in Group 1.
Element Symbol Atomic Number Electronic configuration
Lithium Li 3 2.1
Sodium Na 11 2.8.1
Potassium K 19 2.8.8.1
 The outer shell contains only one electron.
 When these elements react, they lose this outer electron.
 In order to lose an electron, the atom requires energy to overcome the electrostatic forces of
attraction between the negatively charge electron and the positively charged nucleus.
 Potassium is the most reactive of the three metals because less energy is required to remove the
outer electron from its atom than is required for sodium or lithium.
1. The size of the atom increases and therefore the outer electron gets further away from the nucleus
2. The outer electron is therefore less strongly attracted to the nucleus.

4. 2.8- explain the relative reactivities of the elements in Group 1 in terms of distance between the outer
electrons and the nucleus.
c) Group 7 elements (Halogens) — chlorine, bromine and iodine
2.9 - recall the colours and physical states of the elements at room temperature.
State Colours
F2 Gas Yellow
Cl2 Gas Green
Br2 Liquid Dark red liquid –red/brown vapour
I2 Solid Dark grey solid – purple vapour
2.10 make predictions about the properties of other halogens in this group
2.11 understand the difference between hydrogen chloride gas and hydrochloric acid