Atomic structure, bonding and periodicity

Question 1

Relative mass and relative charge of a proton

Answer 1

Relative mass: 1

Relative charge: +1

Question 2

Relative mass and relative charge of a neutron

Answer 2

Relative mass: 1

Relative charge: 0

Question 3

Relative mass and relative charge of a electron

Answer 3

Relative mass: 1/1840

Relative charge: -1

Question 4

What is mass number?

Answer 4

2. Mass number = protons + neutrons

Question 5

What is the formula for relative atomic mass?

Answer 5

(Average mass of an atom x 12) / mass of 1 atom of Carbon 12

Question 6

What are isotopes?

Answer 6

4. Isotopes are atoms of the same element with the same number of protons and electrons but a different number of neutrons.

Question 7

What is the formula for relative atomic mass?

Answer 7

((Mass of isotope 1 x abundance) + (mass of isotope 2 x abundance) etc) / total abundance

Question 8

What is the maximum number of electrons in the s, p and d subshell?

Answer 8

s :2

p: 6
d: 10

Question 9

What is the subshell order?

Answer 9

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 5d

Question 10

Why are electrons lost from the 4s subshell before the 3d subshell in ions?

Answer 10

In ions the 4s electrons are lost before the 3d because they are higher in energy.

Question 11

What is an ionic bond?

Answer 11

1. Ionic bond is the strong electrostatic attraction between oppositely charged ions.

Question 12

When does ionic bonding occur?

Answer 12

It occurs between atoms with very different electronegativities. Eg: NaCl, MgO, Li2(SO4)

Question 13

What is a covalent bond?

Answer 13

A covalent bond is a shared pair of electrons.

Question 14

When do covalent bonds occur?

Answer 14

• It occurs between atoms of similar electronegativities.

Question 15

What is a coordinate bond?

Answer 15

Coordinate bond is a shared pair of electrons, where both electrons come from one atom.

Question 16

What is metallic bonding?

Answer 16

Metallic bonding is a strong electrostatic attraction between positive metal ions and delocalised electrons.

Question 17

When does the strength of metallic bonding increase?

Answer 17

• charge on the ion increases
• number of delocalised electrons increases
• atomic radius decreases

Question 18

Why are metals malleable?

Answer 18

Metals are malleable because the layers of atoms can slide over each other because they are all the same size.

Question 19

What is a molecule?

Answer 19

A molecule is two or more atoms joined by a covalent bond

Question 20

What have intermolecular forces acting between them?

Answer 20

Only molecules and graphite have intermolecular forces between them. They occur between all molecules and atoms of noble gases.

Question 21

What are the three types of intermolecular forces?

Answer 21

• Van der Waals Forces
• Hydrogen bonding
• permanent dipole-dipole forces.

Question 22

What is hydrogen bonding?

Answer 22

Hydrogen bonding is the attraction between slightly positive hydrogen and a lone pair of electrons on either: fluorine, oxygen or nitrogen.
Eg: HF, H2O, NH3 and alcohols

Question 23

When do van der Waals forces act?

Answer 23

Van der Waals forces act between all atoms and molecules.

Question 24

When do permanent dipole-dipole forces act?

Answer 24

Occurs between
molecules of differing electronegativities (polar molecules).
Eg: HCl

Question 25

What is periodicity?

Answer 25

Periodicity is a trend across a period that is repeated across all periods.

Question 26

What is the trend in atomic radius across a period?

Answer 26

Atomic radius decreases across a period due to electrons being added to the same shell and increasing numbers of protons leading to greater attraction between protons and outer shell electrons.

Question 27

What is electronegativity?

Answer 27

Electronegativity is the ability of an atom to withdraw electron density from a covalent bond.

Question 28

What is the trend in electronegativity across a period?

Answer 28

Electronegativity increases as you go across a period due to more protons being added to the same shell and decreasing atomic radius, leading to a greater attraction to the bonding pair of electrons.

Question 29

What is ionisation energy?

Answer 29

Ionisation energy is the energy required to remove a mole of electrons from a mole of atoms in the gaseous state.

Question 30

What is the trend in ionisation energy across a period?

Answer 30

Ionisation energy generally increases as you go across a period because atomic radius decreases and there are increasing numbers of protons.

Question 31

Where are the two exceptions to the trend in the ionisation energy across a period?

Answer 31

At aluminium and at sulfur.

Question 32

Why does the ionisation energy decrease at aluminium?

Answer 32

The outer electrons are the 3p sublevel which is further from the nucleus than the outer 2s electrons in Mg and therefore higher in energy, so less energy is needed to remove it.

Question 33

Why does the ionisation energy decrease at sulfur?

Answer 33

There are paired electrons in the 3p orbital which repel each other and so an electron takes less energy to remove.