1. Atomic structure & Periodic table Flashcards
Define mass number
The mass number is the sum of protons and neutrons in an atom
Define the atomic number
The number of protons in an atoms nucleus. It also equals the number of electrons in a neutral atom
How do you work out the number of neutrons
number of neutrons= mass number - atomic number
What are isotopes
Isotopes are atoms with the same number of protons but different number of neutrons, resulting in a different mass number
Define Relative Atomic Mass
Relative atomic mass is the weighted average mass of all the isotopes of an element compared to 1/12 of the mass of carbon-12
Define Relative Isotopic mass
Relative isotopic mass is the mass of a single isotope in an element compared to 1/12th of the mass of carbon-12
Define Relative Molecular Mass
Relative molecular mass is the mean mass of a molecule of a compound compared to 1/12 of the mass of carbon-12
What is Atomic radius
Atomic radius is the distance from the nucleus to the outermost electron shell in an atom
Explain the atomic radius down a group
- Increases down a group as electrons are added each time, increasing the number of electron shells
- increases the distance between the nucleus and the other electrons, even though nuclear charge also increases
Explain atomic radius Across a period
The atomic radius decreases across a period due to an increased nuclear charge - more protons in the nucleus. This pulls electrons closer to the nucleus while shielding remains the same
Define first ionisation energy
First ionisation energy is the energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of positive ions
Why is the second ionisation energy greater than the first ionisation energy?
The second ionisation is always greater than the first because it removes an electron from a positive ion, not a neutral ion.
What does a large jump in successive ionisation energies mean?
An electron is being removed from an inner shell
Why does ionisation energy drop between groups 2&3
The change in sub-shell structure causes the drop in energy as 3p is further away from the nucleus than 3s
Why does ionisation energy drop between 5&6
It drops due to electron repulsion. The opposite spin causes the electrons to repel, this causes the energy to drop for a few seconds
Explain the First ionisation energy down a group
The first ionisation energy decreases down a group due to an increasing atomic radius and electron shielding, which reduces the effect of the electrostatic forces of attraction
Explain the first ionisation energy across a period
First ionisation energy increases across a period due to a decreasing atomic radius, and greater forces of electrostatic attraction
Explain the Aufbau Principle
Electrons fill the lowest available energy orbitals first
Explain Hund’s rule
When electrons occupy orbitals of equal energy, one electron goes into each orbital before pairing begins. This minimises electron repulsion
Explain Paulis exclusion rule
No two electrons in the same atom can have the same set of four quantum numbers
Define Periodiciity
Periodicity is a trend or pattern of repeating physical and chemical properties
Define Electronegativity
The ability of an atom to attract itself towards a bonding pair of electrons from a covalent bond
Define melting point & boiling point
Melting point is the ease at which a solid turns into a liquid, and then from a liquid to a gas
