Ionization energy is a measure of how hard it is to pull an electron away from an atom.
The stronger the pull between the nucleus and the electrons, the higher the ionization energy.
First ionization energy is the energy needed to pull the first electron away from an atom.
Second ionization energy is the energy needed to pull a second electron away from an atom. An element’s second ionization energy is always greater than its first ionization energy.
This pattern is true for higher ionization energies as well.
You get the picture.
If an atom has two valence electrons (like Ca), its second ionization energy will be greater than the first, but the third ionization energy will be much, much greater. This is because the third electron that you are trying to remove is in a closer energy level and is held by the nucleus with much more force.
Ionization energy increases as you go from left to right on the periodic table because there are more protons in the nucleus pulling in on the valence electrons
Ionization energy also increases as you move up the periodic table because the valence electrons are closer to the protons in the nucleus
Of all the elements, Helium has the highest ionization energy (is hardest to steal from), and Francium has the lowest (is easiest to steal from).
In general, the closer an element is to Helium on the periodic table, the higher its ionization energy, and the closer to Francium the lower its ionization energy. Keep in mind, however, that this is just a generalization; to be certain; you have to check the periodic table. On your periodic table, 1st ionization energy is the blue number, second from the top on the left side of the box on the back side of the table
The size of an atom (atomic radius) tends to decrease as you move from left to right on the periodic table because the extra protons in the nucleus pull all the energy levels inward
The size also decreases as you move up the periodic table because there are fewer energy levels
Of all the elements, Helium is the smallest, and Francium is the largest.
In general, the closer an element is to Helium on the periodic table, the smaller its atomic radius, and the closer to Francium the larger its atomic radius. Keep in mind, however, that this is just a generalization; to be certain; you have to check the periodic table. On your periodic table, atomic radius is just below the 1st ionization energy.
