Unit 2: Section 1 - Periodicity CDS *

Question 1

what do all the elements in a period have?

Answer 1

they all have the same number of electron shells

Question 2

what do all the elements in a group have?

Answer 2

they all have the same number of electrons in their outer shell so they all have similar properties

Question 3

what does the group number tell you?

Answer 3

the number of electrons in the outer shell

Question 4

what happens to the atomic radius across a period?

Answer 4

same shells
same shielding
more protons
stronger electrostatic forces of attraction between nucleus and outer electrons
atomic radius decreases

Question 5

why does the atomic radius decrease with more protons?

Answer 5

the stronger the positive charge, the more the outer electrons are pulled towards the nucleus, making the atom smaller. (greater charge density)

Question 6

what happens to melting points across a period?

Answer 6

they vary as they depend on the structure and bonding of the elements.

Question 7

which types of bonding of elements have the highest and lowest melting points?

Answer 7

giant covalent lattice - highest
metallic
simple molecular - lowest

Question 8

what happens to the melting points of metals across a period?

Answer 8

more protons
more delocalised electrons
stronger electrostatic forces of attraction
melting point increases

Question 9

why does silicon have the highest melting point in period 3?

Answer 9

its macromolecular, with a tetrahedral structure. many strong covalent bonds link atoms together
a lot of energy is required to break these bonds

Question 10

what happens to the melting points of molecular substances across a period?

Answer 10

it depends on the number of atoms in the molecule.
the more atoms
the more electrons
the stronger van der Waals forces between molecules
the higher the melting point

Question 11

what happens to ionisation energy across a period?

Answer 11

ionisations generally increase across a period:
more protons
stronger electrostatic forces of attraction
the more energy required to remove an electron

Question 12

what happens to ionisation energy between group 2 and 3?

Answer 12

the outer electron is in a new orbital - p1 compared to s2.
in a higher energy level
so ionisation energy lower

Question 13

what happens to ionisation energy between group 5 and 6?

Answer 13

the outer electron is sharing a sub-shell with another electron in p4
repulsion between electrons
lower ionisation energy

Question 14

what happens to atomic radius down a group?

Answer 14

more shells
more shielding
weaker electrostatic forces of attraction
atomic radius increases

Question 15

what happens to ionisation energy down a group?

Answer 15

more shells
more shielding
weaker electrostatic forces of attraction
ionisation energy decreases