Atomic Structure (Alan's Notes)

Question 0

What is a covalent bond?

Answer 0

Covalent bonds are where non-metals share electrons and create a covalently bonded molecule.

Question 1

What makes a noble gas stable?

Answer 1

The amount of electrons in the outer shell. 8 electrons is a stable amount.

Question 2

What is a molecule?

Answer 2

It consists of two or more atoms bonded together by covalent bonds.

Question 3

List examples of Diatomic gases.

Answer 3

O2, Cl2, S2, N2.

Question 4

What are atoms composed of?

Answer 4

Protons, neutrons and electrons.

Question 5

When does the number of protons equal the number of electrons?

Answer 5

In an electrically neutral atom.

Question 6

Define isotopes.

Answer 6

They are atoms of the same element that have different numbers of neutrons in the nucleus.

Question 7

What are ions?

Answer 7

Ions are charged atoms.

• Positive ions have more protons than electrons.
• Negative ions have more electrons that’s protons.

Question 8

What are valence electrons?

Answer 8

They are electrons in the outermost shell of an atom.

Question 9

How are the elements arranged in the periodic table?

Answer 9

They are arranged in order of increasing atomic number.

Question 10

What are periods?

Answer 10

They are horizontal rows of elements in the periodic table.

Question 11

What are groups?

Answer 11

They are vertical columns of elements in the periodic table.

•Elements in the same group in the periodic table have the same outer-shell electron arrangement and they share some similar properties.

Question 12

What are the trends in the 1st Ionisation energy?

Answer 12

1. The atoms nuclear charge
2. The distance between the nucleus and outermost electrons - ATOMIC RADIUS
3. Shielding by inner electrons

Question 13

What does the trends in the 1st Ionisation energy have to do with the atoms nuclear charge?

Answer 13

• Depends upon it’s # of protons
• Increasing nuclear charge means electrons are attracted more strongly to the nucleus and so Ionisation energy increases with increasing nuclear charge.

Question 14

What does the trends in the 1st Ionisation energy have to do with the distance between the nucleus and outermost electron - ATOMIC RADIUS?

Answer 14

• As the atomic radius increases so the strength of attraction between the nucleus (+) and the outer electron (-) decreases.
• Thus Ionisation energy decreases with increasing atomic radius.

Question 15

What does the trends in the 1st Ionisation energy have to do with the shielding by inner electrons?

Answer 15

• Each electron in the atoms electron cloud repels each other.
• The more electrons there are between the outer electrons and the nucleus the more easily the electron is removed and the lower the Ionisation energy.

Question 16

When does successive Ionisation energies increase for an atom?

Answer 16

• Gradually as the charge in the ion being formed increases.

* Markedly when the electron is removed from a shell closer to the nucleus.

Question 17

How is the core charge determined?

Answer 17

It is determined by subtracting the number of inner-shell electrons from the number of protons in the nucleus.

Question 18

What do the atomic radius, Ionisation energy and electronegativity of an element depend on?

Answer 18

They depend on the core charge experienced by the outermost electrons and the average distance of these outermost electrons from the nucleus.

Question 19

What is the atomic radius?

Answer 19

It is a measure of the size of its atom usually the mean or typical distance from the nucleus to the boundary of the surrounding cloud of electrons.

Question 20

How is the elements on a periodic table arranged according to it’s atomic radius?

Answer 20

They increase down a group and decrease across a period.

Question 21

What causes an unusual decrease in the atomic radius? (Elements further to the right of the period)

Answer 21

Higher nuclear charge increases the attraction of electrons bringing them closer to the nucleus thus resulting in a decreased in atomic radius.

Question 22

What causes the increase in atomic radius down a group?

Answer 22

It is due to the higher shell number of the outer electrons for elements lower in a group.

• Electrons in higher shells are generally further away from the nucleus and this causes the atoms further down a group to have a larger radius.

Question 23

What is the atomic radius of a metal defined as?

Answer 23

Being half the distance between the centres of two adjacent atoms in the metallic lattice.

Question 24

What is the atomic radius for non metal atoms that form diatomic molecules?

Answer 24

It is half the distance between the centres of two bonded atoms.

Question 25

Define Ionisation energy.

Answer 25

It is the energy required to remove the most loosely bound electron from an atom, in the gaseous phase.

Question 26

How does the Ionisation of energy work?

Answer 26

It meanders the minimum amount of energy needed to remove the single most loosely bound electron from an atom in the neutral gaseous state.

Question 27

How are the elements arranged according to the first Ionisation energy in the periodic table?

Answer 27

They decease down a group and increase across a period.

Question 28

Define electronegativity.

Answer 28

The ability of an atom in a molecule to attract electrons to itself. It is a measure of the electron-attracting power of an atom in a molecule. •electronegativity decrease down a group and increases across a period.

Question 29

Why do non-metal elements generally have the highest values of electronegativity?

Answer 29

This is to be expected as the elements typically gain electrons to form negative ions.

Question 30

Why do metals have low electronegativity ?

Answer 30

Because within the periodic table there is a general trend of increasing electronegativity from left to right in any period. Down any group the electronegativities show a gradual decrease.