H Chem - Periodicity

Front

How are elements arranged in the periodic table?

Back

Elements are arranged in the periodic table in order of increasing atomic number.

Front

What does the periodic table allow chemists to do?

Back

The periodic table allows chemists to make accurate predictions of physical properties and chemical behaviour for any element, based on its position.

Front

What are groups in the periodic table?

Back

Groups are vertical columns within the table that contain elements with similar chemical properties resulting from a common number of electrons in the outer shell.

Front

What are periods in the periodic table?

Back

Periods are rows of elements arranged with increasing atomic number, demonstrating an increasing number of outer electrons and a move from metallic to non-metallic characteristics.

Front

How are the first 20 elements in the periodic table categorized?

Back

The first 20 elements are categorized according to bonding and structure: metallic (Li, Be, Na, Mg, Al, K, Ca), covalent molecular (H2, N2, O2, F2, Cl2, P4, S8, fullerenes like C60), covalent network (B, C - diamond, graphite, Si), and monatomic (noble gases).

Front

What is covalent radius?

Back

Covalent radius is a measure of the size of an atom. The covalent radius decreases across a period due to the increasing nuclear charge. The covalent radius increases down a group due to the extra energy levels added and the screening/ shielding of the inner electrons from the increasing nuclear charge. The atom is therefore less contracted

Front

What is the first ionisation energy?

Back

The first ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms.

Front

What do the second and subsequent ionisation energies refer to?

Back

They refer to the energies required to remove further moles of electrons from gaseous IONS

Front

How can trends in ionisation energies be explained across a period?

Back

Ionisation energy increases across a period due to the increasing nuclear charge. The outer electrons are strongly attracted to the nucleus so it requires lots of energy to remove this mole of electron.

Front

What happens to the ionisation energy down a group?

Back

The ionisation energy decreases due to the outer electrons being further away from the attraction of the nucleus. The inner electrons also shield the outer electrons from the increasing nuclear charge. Therefore it requires less energy to remove one mole of electrons