Chemistry Exam Revision

Core Charge Definition

the attraction between valence electrons and the nucleus.

Core Charge Trends

Down: core charge remains constant, as number of valence electrons remains constant.

Across: core charge increases as number of valence electrons increases, this means there is greater attraction to the nucleus.

Electronegativity definition

ability of an atom to attract electrons towards itself

Electronegativity trends

Down: decrease as core charge and valence electrons remains constant, however no. of shells increases. This means valence electrons are less strongly attracted to the nucleus as they are further away and there is a higher atomic radius.

Across: increases as no. of shells remains constant but core charge and valence electrons increases. This means valence electrons are more strongly attracted to the nucleus

Atomic Radius definition

distance between the nucleus and the valence electrons

Atomic radius trends

Down: increases as core charge and valence electrons remains constant but no. of shells increases. This means there is more distance between valence electrons and the nucleus.

Across: decreases as no. of shells remains constant but core charge and valence electrons increases. This means valence electrons are more strongly attracted to nucleus causing it to become closer together.

First Ionisation energy definition

the energy required to remobe an electron from an atom

First Ionisation energy trends

Down: decreases as core charge and valence electrons remains constant but no. of shells increases. This means less energy is needed to remove valence electrons as they are less strongly attracted to the nucleus.

Across: increases as no. of shells remains constant but core charge and valence electrons increases. This means more energy is required to remove valence electrons as they are more strongly attracted to the nucleus.

Metallic Character Definition

level of reactivity of a metal

Metallic character trends

Down: increases as atoms have lower ionisation energy, this means less energy is required to remove electrons to form cations.

Across: decreases as atoms have high ionisation energy, this means more energy is required to remove electrons to form cations.

Non-metal reactivity definition

ability of non-metals to attract electrons to its nucleus.

Non-metal reactivity trends

Down: decreases as electronegativity also decreases. This means it will be harder for non-metals to gain electrons.

Across: increases as electronegativity also increases. This means it will be easier for non-metals to gain electrons.

High MP and BP (metallic bonding)

has a sea of free moving delocalised electrons, this means there is stronger electrostatic attraction. Hence more energy is required to break bonds between the lattice.

Conduct electricity (metallic bonding)

has free moving delocalised electrons.

Malleable and Ductile (metallic bonding)

the lattice layers are able to move past one another without disrupting the electrostatic attraction between cations and delocalised electrons.

High density (metallic bonding)

the cations are closer together due to the electrostatic attraction.

Heat conductors (metallic bonding)

heat is stored in delocalised electrons, this means it cant melt and therefore can conduct heat as energy is easily transferred

Lustrous (metallic bonding)

has free moving sea of delocalised electrons which are able to reflect light.

Brittle (ionic bonding)

when force is applied the lattice misaligns and like charges are placed next to each other causing a repulsion and the substance to break.

High MP and BP (ionic bonding)

strong electrostatic attraction between positive cations and negative anions means more heat energy is required to break bonds in the lattice.

Conduct electricity solid (ionic bonding)

is made up of cations and anions arranged in a lattice structure. To conduct electricity substances need free-moving charged particles. In solids there are no free moving charged particles, hence it wont conduct electricity.

Conduct electricity molten (ionic bonding)

is made of cations and anions that are free moving. To conduct electricity substances need free-moving charged particles. In molten there are free moving charged particles hence it will conduct electricity.

soluble in water (ionic bonding)

they can form hydrogen dipole-dipole bonds with water making it soluble.

What makes a molecule polar?

there is a difference in electronegativity, as one atom has a higher ability to attract electrons towards itself this means the partial charges do not cancel out, causing the molecule to be polar.

What makes a molecule non-polar?

there is no difference in electronegativity, and the partial charges do cancel out causing the molecule to be non-polar.

what does each partial sign mean

Partially negative means it is more electronegative and partially positive means it is less electronegative.

MP and BP trend carbon chain (organic chem)

As chain length increases, number of dispersion forces also increases. This means that the intermolecular forces are stronger between molecules, and hence more energy is required to break bonds, therefore there is a higher boiling points as chain length increases.