1. Atomic Concepts How the building blocks of life work; and where they came from Brought to you by Erica Stevens

2. Words to Know Atom Atom: the smallest particle of an element that has the chemical identity of that element Electrons Electrons: Negatively charged particles outside of the nucleus Protons Protons: carry the positive charge of the nucleus Neutrons Neutrons: Have no electrical charge (neutral) and are also found in the nucleus

3. Early Models of the Atom J. J. Thomson used cathode rays to establish his “plum-pudding” model – Negative charges are distributed evenly throughout an atom’s positively charged interior. Ernest Rutherford shot a beam of alpha particles at a piece of gold foil and most passed through; but some scattered – An atom is mostly empty space in which there is a small dense positive nucleus with electrons orbiting it.

5. Ions When an atom loses or gains one or more electrons it acquires a net electrical charge and is called an ion A positively charged ion has more protons than electrons A negatively charged ion has more electrons than protons Net charge = #protons - #electrons Mg 2+ has how many electrons?

6. Isotopes Atoms that have the same number of protons but different numbers of neutrons Chemical characteristics of isotopes are basically the same Mass is the big difference Atomic mass on the periodic table is a weighted average mass based on natural abundance

7. The Nucleus Like charges repel each other; so how do all those protons make up the nucleus? Strong Nuclear force is an attractive force that is strong enough to over come proton-proton repulsions and thus hold protons and neutrons together in the nucleus There is a stable ratio of protons to neutrons which is not always 1:1 once the atomic number increases (more about that in nuclear chemistry)

8. The Excited State Niels Bohr decided that when electrons are given a specific amount of energy they can become excited and jump to a higher energy level They quickly fall back down to the ground state and release this energy in the form of light

9. And Finally……