Atomic Size (Pre-IB SC 9)
What happens to the atomic size as you go down a group?
The atomic size increases.
Why does the atomic size increase going down a group?
- The elements have increasing energy shells
- The greater the number of shells, the farther the valence electrons are from the nucleus and the larger the atom is
What happens to atomic size moving left to right across a period?
The atomic size decreases.
Why does the atomic size decrease going across a period?
- Elements have increasing NUMBERS of electrons in their valence shells, but the number of OCCUPIED VALENCE SHELLS stays the same
- The number of protons in the nucleus increases so EFFECTIVE NUCLEAR CHARGE decreases, pulling the valence electrons tightly to the nucleus
Why does reactivity increase moving down the table?
- In a group, the valence electrons stays the same
- As you go down the group, the atomic size increases
- The valence electrons become farther away from the nucleus, so the pull of the nucleus is weaker and the electrons are easier to remove