introduction to a level chemistry

What are sub-shells in terms of an atoms energy level

Each energy level of an is split into sub-levels called "sub-shells". The first 3 sub-shells are called: "s", "p" and "d". The first energy level has only one sub-shell, an "s" level, therefore it only holds two electrons. The second energy level holds 8 electrons, the "s" level holds two electrons and the remaining 6 electrons are in the "p" level

The s-block and the p-block of the periodic table

Groups 1 and 2 of the periodic table (the alkali metals) are called the s-block elements. Their outer electrons are "s" sub-shell energy levels, meaning they can accommodate up to 2 electrons. Group 3 and 0 are p-block elements, there outer electrons are in energy levels called "p" sub-shells, meaning they can accommodate up to 6 electrons. The only exception in group 0 is helium, which is an s-block element

what is ionisation energy

The energy you need to remove the first outer electron is called the first ionisation energy. Full definition: the first ionisation energy is the energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms. The ionisation energy is always a positive number as it needs to be "added" to overcome the attraction between the negative electron and the positively charged nucleus. The lower the ionisation energy, the easier it is to remove the outer electron and form an ion

3 things that affect ionisation energy

1. nuclear charge: the more protons there are in the nucleus, the stronger the positive charge is , forming a stronger attraction with electrons.

2.Distance from the nucleus: Attraction decreases with distance, so an electron closer to the nucleus will be more strongly attracted than one further away

3. Shielding: electrons in shells closer to the nucleus can stop the outer electrons from feeling the full force of the nuclear charge. The inner electrons are said to "shield" the outer electrons from the nucleus, so more inner electrons = more shielding = weaker attraction between outer electrons and nucleus = lower ionisation energy