(y3 but oh well) periodic table

Question 1

Across the period, there is a general decrease in atomic radii. Explain why.

Answer 1

Nuclear charge increases as number of protons increases successively from one element to the next. Number of electrons remain the same as successive electrons are added to the same principal quantum shell. Effective nuclear charge increases down the period, electrostatic forces of attraction between the valence electron and the nucleus increases and the size of the electron cloud decreases. Hence, atomic radii decreases across the period.

Question 2

Down the group, there is a general increase in atomic radius. Explain why.

Answer 2

Number of filled principal quantum shells increases. Distance between the nucleus and the valence electrons increases. Electrostatic forces of attraction between valence electron and nucleus decreases and the size of the electron cloud increases. Hence, atomic radii increases down the group.

Question 3

Some properties of group I metals:

• They are the ____ ______ of all the metals
• They have generally ___ densities and melting points
• They react _____ with water

Answer 3

Some properties of group I metals:

• They are the most reactive of all the metals
• They have generally low densities and melting points
• They react violently with water

Question 4

Every alkali metal reacts with cold water (explosive in hot water/steam), releasing _______ ____ and producing a solution of _____ ______ that is alkaline.

Answer 4

Every alkali metal reacts with cold water (explosive in hot water/steam), releasing hydrogen gas and producing a solution of metal hydroxide that is alkaline.

Question 5

For the equation of metal + water –> metal hydroxide + hydrogen gas, what are some observations?

Answer 5

• Effervescence is observed due to production of hydrogen gas
• Darting of metal piece on the surface of the water
• Beaker feels warm (heat is produced during the reaction)

Question 6

Reactivity of group I elements increases down the group. Explain why.

Answer 6

Down the group, number of filled principal quantum shells increases. Distance between the nucleus and the valence electrons increases. Despite the increasing nuclear charge, electrostatic forces of attraction between the nucleus and the valence electrons decreases. Thus, energy required to remove the valence electrons decreases and reactivity of the metals increases.

Question 7

Melting points of group I elements ______ down the group.

Answer 7

Melting points of group I elements decreases down the group.

Question 8

Densities of the elements increases down the group. Explain why.

Answer 8

Relative atomic mass increases down the group. Since density = mass/volume, when the mass increases, density increases.

Question 9

Some properties of group VII elements:

• They all exist as _____ _____ bonded molecules with the formula X_.
• They are typical _______ with ___ melting and boiling points

Answer 9

Some properties of group VII elements:

• They all exist as diatomic covalently bonded molecules with the formula X2.
• They are typical non-metals with low melting and boiling points

Question 10

Reactivity of group VII elements ______ down the group.

Answer 10

Reactivity of group VII elements decreases down the group.

Question 11

Melting and boiling point of group VII elements increases down the group as seen in the physical state of elements changing from gas –> liquid –> solid. Explain why.

Answer 11

As the molecular mass of each molecule increases, the strength of the intermolecular forces of attraction (van der Waals’ forces of attraction) increases. More energy is thus needed to overcome the stronger intermolecular forces of attraction between iodine molecules than those between bromine, chlorine, fluorine molecules.

Question 12

Colour of group VII elements gets ______ down the group.

Answer 12

Colour of group VII elements gets darker down the group.

Question 13

Halogens undergo ________ reactions with halide (halogens react with metals to form salts called halides) solutions.

Answer 13

Halogens undergo displacement reactions with halide (halogens react with metals to form salts called halides) solutions.

Question 14

A _____ reactive halogen will displace a _____ reactive halogen from its compound.

Answer 14

A more reactive halogen will displace a less reactive halogen from its compound.

Question 15

Some properties of transition metals:

• They have _____ melting and boiling points + densitiies
• They have ______ oxidisation states in their compounds
• They form _______ compounds

Answer 15

Some properties of transition metals:

• They have high melting and boiling points + densities
• They have variable oxidisation states in their compounds
• They form coloured compounds