How to first ionization energies vary within groups and across periods

Ionisation energy increases along a period but decreases down a group

Explanation:

As you go along the period, the amount of protons in the nuclear increases. This causes nuclear attraction to increase meaning the attraction between the protons and the electrons is higher. This causes the electrons to be held more tightly to the nucleus meaning they are harder to remove. As well as that, the shielding stays the same along a period since the electrons are being added to the same shell, just different orbitals. Overall this makes it harder to remove an electron as you go along a period causing the ionisation energy to increase along a period.

On the other hand when you go down a group, the atomic radius increases. This is because the electrons are added to new shells which are further away from the nucleus, this also causes shielding to increase as there are more shells. This means the outer electrons being removed are held less tightly by the protons in the nucleus meaning they are easier to remove. This means that the ionisation energy decrease down a group.

chemical energy is stored in the chemical bonds of atoms and molecules. it can only be seen when it is released in a chemical reaction. when chemical energy is released, the substance from which the energy came is often changed into an entirely different substance.

this chemical reaction releases energy in the form of light and heat. chemical energy is the potential energy stored in the arrangement of atoms within molecules. breaking chemical bonds requires energy, while forming new chemical bonds releases energy.

the atp molecule can store energy in the form of a high energy phosphate bond joining the terminal phosphate group to the rest of the molecule. in this form,energy can be stored at one location, then moved from one part of the cell to another, where it can be released to drive other biochemical reactions.

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