Periodicity

Question 1

covalent radii definition

Answer 1

half the distance between the nuclei of two covalently bonded atoms.

Question 2

covalent radii trend across a period

Answer 2

decreases because the nuclear charge is increasing and so the electrons in the filled outer shells are pulled in closer to the nucleus.

Question 3

covalent radii trend down a group

Answer 3

increases because the number of electron shells is increasing so atomic size increases.

Question 4

first ionisation energy definition

Answer 4

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

Question 5

second ionisation energy definition

Answer 5

the energy required to remove one mole of electrons from one mole of gaseous 1+ ions.

Question 6

ionisation energy trend across a period

Answer 6

increases because the nuclear charge is increasing and so the electrons are more strongly attracted to the nucleus resulting in more energy required to remove an electron.

Question 7

ionisation energy trend down a group

Answer 7

decreases because an electron is being removed from an electron shell which is further from the nucleus. (weaker electrostatic attraction)
the inner shells of electrons ‘shield’ the outer electrons from the nuclear charge meaning they are less strongly attracted to the nucleus resulting in less energy being required to remove an electron.

Question 8

electronegativity definition

Answer 8

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

Question 9

electronegativity trend across a period

Answer 9

increases as nuclear charge is also increasing in this direction which creates a stronger electrostatic attraction between the nucleus and the negative bonded electrons.

Question 10

electronegativity trend down a group

Answer 10

decreases because the atomic size increases due to the increases number of electron shells. The increase in shells of electrons ‘shield’ the bonded electrons from the nuclear charge meaning they are less strongly attracted to the atoms.

Question 11

screening effect

Answer 11

when inner electrons shield an outer electron from the attractive effect of the nucleus and less energy is needed to remove the outer electrons as a result.

Question 12

the periodic table

Answer 12

• invented by Dimitri Mendeleev in 1869
• elements arranged in order of increasing atomic number
• mp, bp and density are periodic in nature
• elements in the same group have similar chemical properties

Question 13

why does it require much more energy to remove an electron from a full electron shell?

Answer 13

• destroys the stability associated with the full arrangement of electrons.
• electron is closer to the nucleus (more strongly attracted)
• harder to remove an electron from a positive ion than an atom.

Question 14

buzz words that should make you think of electronegativity in exam

Answer 14

“attraction for bonding electrons”

Question 15

group in periodic table

Answer 15

• vertical columns
• similar chemical properties
• common number of electrons in outer shell

Question 16

period in periodic table

Answer 16

• horizontal rows
• increasing atomic number
• increasing number of electrons in outer shell
• move from metallic to non-metallic characteristics