Atoms

What is meant by the term relative atomic mass?

What is meant by the term relative atomic mass?

The weighted mean mass of an atom of an element relative to an atom of carbon-12 having a mass of exactly 12 units.

What is meant by the term molecular mass?

The weighted average of the mass of a molecule relative to an atom of carbon-12 having a mass of exactly 12 units.

What is meant by the term relative isotopic mass?

The mass of an atom of an isotope on a scale relative to an atom of carbon-12 having a mass of exactly 12 units.

What is meant by the term relative formula mass?

The weighted average of the masses of the formula units relative to an atom of carbon-12 having a mass of exactly 12 units.

Define the mole

The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of carbon-12.

What is meant by the term empirical formula?

The simplest whole number ratio of atoms of each element present in a compound.

How do protons behave in an electric field?

Protons are deflected towards the negative plate in an electric field.

How do neutrons behave in an electric field?

Neutrons are not affected by an electric field due to their lack of charge.

How do electrons behave in an electric field?

Electrons are deflected towards the positive plate in an electric field. The deflection is greater than protons as the electron has a smaller mass.

Where is most of the mass of an atom concentrated?

In the nucleus

What does the atomic number represent?

The atomic number is equal to the number of protons in the nucleus of an atom of an element.

What does the mass number represent?

The mass number is equal to the sum of the numbers of protons and neutrons in the nucleus of an atom of an element

What are isotopes?

Atoms of the same element with the same number of protons but a different number of neutrons

What is an orbital?

A region that holds up to 2 electrons, with opposite spin

What rules do electrons follow when filling up orbitals?

Electrons always occupy the lowest energy orbital available.
Generally, electrons only pair up when there are no empty orbital of the same energy level as the half-filled orbitals.

What is meant by the term first ionisation energy?

The energy required to remove an electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.

Is first ionisation energy exothermic or endothermic?

Endothermic

What is the trend in first ionisation energy across periods 2 and 3?

first ionisation energy increases.

Why does first ionisation energy increase across a period?

Nuclear charge increases.
Atomic radius decreases.
Shielding remains the same.
As a result of these factors, electrostatic attraction increases, so more energy is needed to overcome these forces to remove an electron from the atom.

What is the trend in first ionisation energy down a group?

ionisation energy decreases.

Why does first ionisation energy decrease down a group?

Nuclear charge increases
Atomic radius increases.
Shielding increases.
Therefore electrostatic attraction decreases, so less energy is needed to overcome these forces to remove an electron from the atom.

What is electron affinity? (

The enthalpy change that accompanies the addition of 1 electron to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions.