Topic 3: Periodicity

Question 1

What is the periodic table arranged according to

Answer 1

Increasing atomic number

Question 2

What does period number represent

Answer 2

The number of energy levels (shells)

Question 3

What is group number

Answer 3

the number of valence electrons

Question 4

Name for group 1, 17 and 18

Answer 4

Alkali metals, halogens and noble gases

Question 5

What are lanthanoids on the periodic table

Answer 5

La to Lu

Question 6

Actinoids on periodic table

Answer 6

Ac to Lr

Question 7

What properties do metalloids have

Answer 7

Those intermediate between those of a metal and a non-metal

Question 8

Chemical and physical properties of a group

Answer 8

Are similar

Question 9

How to find atomic radius and its trend

Answer 9

Half of the distance between the nuclei of two bonded atoms of the same element

radius increases down a group because outermost electrons are in higher energy levels

radius decreases across period because there are an increasing amount of protons and positive charge - attracts energy level closer

Question 10

Ionic radius trend

Answer 10

Important to consider cations vs anions
Groups 1,2,3 that form cations have smaller radius because they have fewer electrons then protons causing the inward pull to be stronger, ion is smaller than parent atom because energy shell has decreased by one

Groups 5, 6, 7 that form anions have bigger ionic radius because they have more electrons than protons + gained an energy shell

Question 11

Melting points across period 3

Answer 11

Na, Mg and Al exhibit metallic bonding –> which strength increases as the number of valence electrons increase

Si –> is a giant covalent structure - so extremely high melting point

P4, S8, Cl 2 are simple molecular structures with weak intermolecular forces of attraction, held together by LDF so the larger the atom the higher the mp

noble gases have very weak forces of attraction

Question 12

Melting point trend down group 1 and group 17

Answer 12

Melting point decreases down group 1, atom becomes larger so strength of metallic bond decreases

Increase down group 17 - intermolecular forces increase down the group (van der waal forces increase with greater atom and more electrons0

Question 13

First ionization energy

Answer 13

Amount of energy required to remove the first electron from an atom in the GASEOUS STATE

Question 14

First ionization energy trend

Answer 14

Decrease down group because greater atomic mass means less hold on the electrons, increase across period because more protons and the extra electrons are added to the same shell

Question 15

Electronegativity

Answer 15

measure of the attraction an atom has for the shared pair of electrons in a covalent bond

Question 16

Electronegativity trend

Answer 16

Decreases down group and increases across period due to increasing protons (F, N and O are the most electronegative) (wow the hydrogen bonding ones)

Question 17

First electron affinity

Answer 17

energy change when an electron is added to an isolated atom in the gaseous state

Values are negative for the addition of the first electron because they want it (exothermic)
the more it wants it the more energy is released

Question 18

Why is group 1 called alkali metals

Answer 18

They all react with water to form an alkali solution of the metal hydroxide and hydrogen gas

Question 19

Chemical properties of group 1

Answer 19

They react by losing their outer electron to form metal ion, are good reducing agents, reactivity increases down group because less energy holding onto the elecctrons.

Question 20

Chemical properties of group 17

Answer 20

React by gaining one more electron to form halide ions, good oxidizing agents, reactivity decreases down group because less pull inwards

Question 21

how to detect halide ions in solution

Answer 21

add silver nitrate solution, forms precipitate of silver halide and can be distinguished by their colour, reacts with light to form silver metal. is the basis of old fashioned film photography.

Question 22

how to distinguish metal from non metals

Answer 22

through chemical properties, metal oxides tend to be basic, whereas non metal oxides are acidic