Periodic Trends

Atomic Radius Measure of how large an atom is. Measured from the nucleus to the outer most energy level.

How does atomic radius change down a group? It increases down the group. Why? Add energy level every time you move down. More Energy levels = more electrons = larger atom

How does atomic radius change across a period? It decreases across the period Why? More protons in the nucleus higher electrical force pulls electrons closer to nucleus.

The Periodic Table and Atomic Radius

Ionization energy Ionization energy is the amount of energy needed to remove an electron from an atom

How does ionization energy change down a group? The ionization energy decreases as you move down a group. Why? The size of the atom increases. Electron is further from the nucleus. Easier to get away – little attraction

How does ionization energy change across a period? The ionization energy increases as you move from left to right across a period. Why? Attraction of the electron to the nucleus increases. Harder to get away – Lots of attraction Nuclear charge (protons) increases while shielding (electrons in lower E.L.) is constant.

Electronegativity: the ability of an atom to attract an electron.

Trends in Electronegativity Electronegativity generally decreases as you move down a group. Why? Electrons further away from nucleus Weaker attraction

Trends in electronegativity Electronegativity increases as you move across a period. Why? Greater attraction of electrons to nucleus Getting closer to full octet Easy to attract another electron.