Unit 1(b) - Periodicity

Question 1

What is a periodic pattern?

Answer 1

A pattern which repeats across a period in the periodic table

Question 2

What did Mendeleev use to arrange the then known elements?

Answer 2

Increasing masses and similar chemical properties

Question 3

How is the modern periodic table arranged?

Answer 3

Increasing atomic number

Question 4

In the modern periodic table, what are trends related to?

Answer 4

Bonding and structure

Question 5

What is the covalent radius of an atom?

Answer 5

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

Question 6

What happens to atomic size as you move across a period?

Answer 6

Atomic size decreases, as the increasing nuclear charge pulls electrons closer to the nucleus

Question 7

What happens to atomic size as you move down a group?

Answer 7

Atomic size increases as an extra electron shell is added, as well as nuclear attraction decreasing due to shielding by inner electrons

Question 8

What is the density of a substance?

Answer 8

It’s mass per unit volume

Question 9

What happens to density as you move across a period?

Answer 9

The general trend is that in any period, density first increases from group 1 to a maximum in the centre, then decreases again towards group 0

Question 10

What happens to density as you move down a group?

Answer 10

Density increases as the mass of the atom is increasing faster than the volume

Question 11

What do melting and boiling points indicate?

Answer 11

The strength of the forces between particles

Question 12

What happens to mps and bps as you move across a period?

Answer 12

Increase from group 1 to group 4 (group 4 elements are covalent networks), then decrease to group 0

Question 13

What happens to mps and bps as you move down group 1?

Answer 13

Melting and boiling points decrease as there is a decrease in attraction between atoms

Question 14

What happens to mps and bps as you move down group 7

Answer 14

Melting and boiling points increase as LDF attractions between molecules increase

Question 15

What is the first ionisation energy?

Answer 15

The energy required to remove one mole of electrons from one mole of gaseous atoms

Question 16

What are the second (and subsequent) ionisation energies?

Answer 16

The energies required to remove further moles of electrons

Question 17

What happens to ionisation energy as you move across a period?

Answer 17

Ionisation energies increase as the increasing nuclear charge pulls electrons closer to the nucleus

Question 18

What happens to ionisation energy as you move down a group?

Answer 18

Ionisation energy decreases as the outer electrons are further from the nucleus, and the shielding effect from the inner electrons reduces the nuclear attraction for outer electrons

Question 19

What is electronegativity?

Answer 19

A measure of the attraction an atom in a bond has for the electrons of the bond

Question 20

Which element is the most electronegative?

Answer 20

Fluorine

Question 21

What happens to electronegativity as you move across a period?

Answer 21

Electronegativity increases as the nuclear charge increases, attracting the electrons more strongly to the nucleus

Question 22

What happens to electronegativity as you move down a group?

Answer 22

Electronegativity decreases because the number of electron shells increases. This means electrons are further from the nucleus and the shielding effect of inner electrons increases

Question 23

What are the properties and structure of elements related to?

Answer 23

The types of bonding present

Question 24

What is a metallic bond?

Answer 24

Electrostatic attraction between positive nuclei and delocalised outer electrons

Question 25

What do metallic structures consist of?

Answer 25

A giant lattice

Question 26

What is metallic bond strength?

Answer 26

A measure of the no. of outer electrons. The greater the no. of electrons, the stronger the metallic bond

Question 27

What are some characteristics of metals?

Answer 27

* Shiny * Malleable * Ductile * Good electrical and heat conductors

Question 28

What happens to metallic character as you move across a period?

Answer 28

It decreases as the mobility of the electrons as they are restricted by the increasing nuclear charge

Question 29

What happens to metallic character as you move down a group?

Answer 29

It increases as outer electrons are held more loosely due to shielding

Question 30

What is the relationship between metallic bond strength and metallic character?

Answer 30

The stronger the metallic bond, the less the metallic character

Question 31

How does the size of metal atoms relate to melting and boiling points?

Answer 31

Smaller metallic atoms have larger melting and boiling points

Question 32

What are metal boiling points dependant on?

Answer 32

* How many electrons are in the outer shell | * No. of electron shells

Question 33

Why are the noble gases stable?

Answer 33

They have full outer electron shells, meaning they are chemically stable and monatomic

Question 34

Why do noble gases form liquids and solids at low temperatures, despite being monatomic?

Answer 34

Weak intermolecular forces - LDF

Question 35

What is LDF?

Answer 35

The attraction between the temporary dipoles caused by uneven distribution of moving electrons

Question 36

What is a dipole

Answer 36

An unequal distribution of charge

Question 37

What is a covalent bond?

Answer 37

The electrostatic attraction between the positive nuclei and the negative shared electrons

Question 38

What kinds of bonding are present in diatomic molecules?

Answer 38

Strong intramolecular bonding (covalent) and weak intermolecular bonding (LDF)

Question 39

Give examples of discrete covalent molecular solids

Answer 39

Phosphorous (P4), sulphur (S8), and carbon (fullerenes)

Question 40

Why are phosphorous and sulphur solids at room temperature, whereas chlorine is a gas?

Answer 40

P and S are larger with more atoms, so have more opportunities for LDF. Chlorine forms diatomic molecules which are gaseous at room temperature

Question 41

What is a covalent network?

Answer 41

A covalent network structure consists of a giant lattice of covalent lay bonded atoms

Question 42

What is the structure of boron?

Answer 42

Boron forms B12 groups which are inter bonded with each other, resulting in an element almost as hard as diamond. It has a very high melting point

Question 43

What two network forms does carbon exist as?

Answer 43

Graphite and diamond

Question 44

What are some properties of graphite?

Answer 44

* Layers of atoms in hexagonal plates * 3/4 outer electrons covalently bonded, 4th outer electron moves within layer * Conducts electricity due to delocalised electron * Soft, slippery, used as a lubricant

Question 45

What are some properties of diamond?

Answer 45

* Regular tetrahedral structure * All 4 outer electrons covalently bonded * Does not conduct electricity * Hardest natural substance, used in cutting tools

Question 46

What element is similar in structure to carbon?

Answer 46

Silicon