1.1 periodicity

Question 1

What is the definition of a group in the periodic table?

Answer 1

• vertical columns within the table
• similar chemical properties resulting f
• common number of electrons in the outer shell

Question 2

What is the definition of a period in the periodic table?

Answer 2

• row of elements arranged
• increasing atomic number
• increasing number of outer electrons
• metallic to non-metallic characteristics.

Question 3

which of the first 20 elements contains metallic bonding?

Answer 3

• Li
• Be
• Na
• Mg
• Al
• K
• Ca

Question 4

Which of the first 20 elements has covalent molecular bonding?

Answer 4

• H2
• N2
• O2
• F2
• Cl2
• P4
• S8
• fullerenes (carbon)

Question 5

which of the first 20 elements have monatomic bonding?

Answer 5

noble gasses

Question 6

Which of the first 20 elements have a covalent network structure?

Answer 6

• B
• C (diamond, graphite)
• Si

Question 7

What is covalent radius?

Answer 7

• a measure of the size of an atom

- it is half the distance between the nuclei of two covalently bonded atoms of an element

Question 8

What is ionisation energy?

Answer 8

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

Question 9

What is electronegativity?

Answer 9

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

Question 10

What is the definition of metallic bonding?

Answer 10

positive metal ions surrounded by a sea of delocalised electrons

Question 11

What created stronger metallic bonds?

Answer 11

the more electrons that are contributed to the delocalised sea of electrons the stronger the metallic bond

Question 12

what are the intra and inter molecular forces between covalent molecules?

Answer 12

intramolecular - covalent

intermolecular - London dispersion forces

Question 13

Explain the structure of carbon in the form of diamond

Answer 13

• covalent network structure
• each carbon atom is covalently bonded to four other carbon atoms
• in a tetrahedral arrangement

Question 14

Explain the structure of carbon in the form of graphite

Answer 14

• each carbon atom forms 3 covalent bonds to neighbouring carbon atoms
• forming layers of hexagonal rings
• the fourth outer electron becomes delocalised between the layers allowing graphite to conduct electricity
• the layers in graphite are held together between weak London dispersion forces

Question 15

Why do monatomic element have low melting points?

Answer 15

the atoms are held together by weak London dispersion forces

Question 16

What are the two trends of covalent radius?

Answer 16

1. going across a period, covalent radius decreases

2. going down a group, covalent radius increases

Question 17

Explain the trend of covalent radius going across a period

Answer 17

• going across a period the nuclear charge increases
• the number of energy levels remains the same
• an increase on nuclear charge results in the electrons being more strongly attracted to the nucleus, decreasing covalent radius

Question 18

explain the trend of covalent radius going down group

Answer 18

• number of filled electron shells increases
• nuclear charge increases too
• the effect of increasing nuclear charge is outweighed by adding energy levels of electrons
• inner electrons shields the outer electrons from the positive nucleus
• so the outer electrons are less strongly attracted to the nucleus
• increasing covalent radius (this effect is also known as screening)

Question 19

What are the two general trends of electronegativity?

Answer 19

1. going down a group, electronegativity decreases

2. going across a period, electronegativity increases

Question 20

Explain the trend of electronegativity going across a period

Answer 20

• going across a period the nuclear charge increases
• this causes the atom to attract bonded electrons more strongly
• resulting in an increase of electronegativity across a period

Question 21

Explain the trend of electronegativity going down a group

Answer 21

• number of filled energy levels increases
• outer electrons are further from the nucleus and are less strongly attracted to the nucleus
• the inner electrons shield the outer electrons from the nuclear charge which means they are less strongly attracted to the nucleus
• resulting in a decrease in electronegativity as you go down the group

Question 22

What are the two general trends of ionisation energy?

Answer 22

1. going down a group, the ionisation energy decreases

2. going across a period, the ionisation energy increases

Question 23

Explain the trend of ionisation energy going across a period

Answer 23

• going across a period, the nuclear charge is increasing
• the outermost electrons are therefore more strongly held and so the energy required to remove them (the ionisation energy) increases along the period

Question 24

Explain the trend of ionisation energy going down a group

Answer 24

• energy levels increases
• the outermost layer is becoming increasingly further from the nuclear attraction
• the inner electrons reduce the attraction of the nucleus for the outermost electrons by creating a shielding effect
• hence, although the nuclear charge is also increasing, the energy required to remove an electron (the ionisation energy) decreases as you go down a group