Atoms

Cannot be subdivided into smaller particles, the smallest unit, the building blocks of life.

Have a charge determined by the balance between the protons and electrons.

• An element Na^- has one more electron than protons.
• An element Na⁺² has two more protons than electron.

Atomic number

The number of protons in the nucleus.

Parts of an Atom

Protons

Denoted by p⁺.

Positively charged, found in the nucleus of an atom.

Neutrons

Denoted by n⁰.

No charge, found the the nucleus of an atom.

Electrons

Denoted by e⁻.

Negatively charged, surrounds the nucleus.

Elements

All of the same type of atoms, together they form an element-on periodic table. Elements are categorized by the unique number of protons found in their nucleus.

Periodic Table

All elements on the periodic table have no charge.

• On the periodic table, they have the same number of electrons as protons.
• On the periodic table, they have the same number of neutrons as protons.

Ions

• Elements that have a charge.
• Elements with a different number of electrons than protons
• If an atom donates an electron, it is positively charged.
• If an atom receives an electron, it is negatively charged.

Atoms like to receive electrons to fill an incomplete outer shell.

Outermost/valence shell determines how/when atoms give/receive electrons.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Shells

A ring/cloud of electrons surrounding the nucleus at a given distance away from the nucleus. Think of the rings around saturn. Each ring of rocks (electrons) is a shell.

Electrons in the outermost shell (valence shell) are easiest to access by the outside world.

Valence Shell

The outermost shell of an atom.

Electron Shell Rules

From inner to outermost (valence) shell, the max number of electrons supported by the shell is 2, 8, 18, 32... An atom that completes the inner-two shells has 10 electrons total.

Happy Atoms

Has a complete outer (valence) shell.

Doesn't want to react.

Unhappy Atoms

Incomplete outer (valence) shell.

Wants to react with another atom to gain/lose electrons.

Transfer of electrons = chemical reaction = forming and breaking of bonds. Each type of bonding is a chemical reaction.

Radioactive Atoms

Nucleus is unstable, easily disrupted, undergoes radioactive decay.

Isotopes

More or fewer neutrons than protons. Changes the atomic mass.

Carbon-12 : 6 protons : 6 neutrons : 6 electrons

Carbon-13 : 6 protons : 7 neutrons : 6 electrons

Molecules

A group of atoms held together by bonds.

Both Oxygen (O₂) and Water (H₂O) are molecules, since they are collections of atoms.

Compounds

A group of atoms help together by bonds, and made up of two or more elements.

Oxygen (O₂) is not a compound, since it is just made up of oxygen.

Water (H₂O) is a compound since it is made up of two different molecules, hydrogen and oxygen.

Bonds

Covalent Bond

• Strong

An electron pair is shared between two atoms. Two electrons in total are shared. One electron is shared by each atom.

Two atoms, each with 9 electrons, 7 in the 2nd shell, will want to share one electron each to bring each up to 8 in the valence shell.

Double-Covalent Bond

• Stronger
• More Rigid

Two electron pairs are shared by each atom. Four electrons total are shared.

Ionic Bond

• Strongest

Ionic bonds are always polar. Giving/receiving of electrons. Oppositely charged ions attract. Ionic bonded compounds form ionic compounds. Ionic compounds are neutrally charged. Electrons are transferred completely and are not shared.

If you rub a balloon and hold above your head, you will notice that your hairs are lifted. What is happening is that your hair and the balloon is charged. One is slightly positive and one is slightly negative. This is what causes them to attract. And this attraction is what lifts your hair up. The hair and balloon situation is somewhat similar to ionic bonds. The ions become charged as a result of the transfer of electrons. Since they are charged, they become attracted to each other (similar as to the hair and balloon).

Ionization

Breaking of ionic bonds of a compound when dissolved in a solvent (usually water).

• Water insulates against the electrostatic charge that holds the compounds together.
• Allows solution to conduct electricity.
  • Molecules break apart into cations and anions.

Table salt dissolves in water.

Hydrogen Bond

Anything involving hydrogen.