Properties of Matter

Element A pure substance that cannot be broken down into simpler substances by ordinary chemical means. Sulfur

Atom The smallest unit of an element that still has the properties of that element. Each element on the periodic table is composed of atoms of only one kind. of only one kind.

Compound A substance made up of atoms of more than one element bonded together. Ex: H 2 O has different properties than H or O alone. Water (liquid) Oxygen (gas)

Molecule The smallest unit of a substance that still has all of the properties of that substance. A molecule can be composed of atoms of a single element (N 2 ), or be a compound (H 2 O). Nitrogen Water

Chemical Formula The chemical symbols and numbers indicating the numbers of atoms contained in the basic unit of a substance. Ex: A water molecule (H 2 O) contains two hydrogen atoms and one oxygen atom.

Chemical Formula A glucose molecule (C 6 H 12 O 6 ) contains 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.

States of Matter

Solid- A form of matter with a definite volume and a definite shape.

States of Matter Liquid- A form of matter that has a definite volume but no definite shape.

States of Matter Gas- A form of matter that has no definite volume and no definite shape.

Melting Point The temperature at which a solid becomes a liquid. (0°C for water)

Boiling Point The temperature at which a liquid becomes a gas. (100°C for water) (100°C for water)

How Do Solids Differ From Liquids? Particles are closer together. (Greater density) Particles have less energy. (Moving slower) Attractive forces between molecules are stronger.

How Do Liquids Differ From Gases? Particles are closer together. Particles have less energy. Attractive forces between molecules are stronger.

Early Ideas About The Atom Democritus (Greek)- Proposed the idea that all matter is composed of very small particles that could not be divided. Atom- “indivisible”

Early Ideas About The Atom John Dalton (b. 1766)- Proposed the idea that all matter is composed of small particles that combine to form molecules.

Dalton’s Atomic Theory 1. Every element is made up of tiny particles called atoms that cannot be broken down into simpler particles. 2. Atoms of the same element are exactly alike. 3. Atoms of different elements can join to form molecules.

Early Ideas About The Atom J.J. Thomson ( )- Proposed the idea that atoms are composed of smaller charged particles that hold the atom together. Opposite charges attract.

Early Ideas About The Atom Ernest Rutherford ( )- Conducted an experiment that provided evidence for the existence of a positively charged nucleus inside of atoms. The mass of an atom is concentrated inside the nucleus.

Early Ideas About The Atom Niels Bohr ( )- Proposed the idea that negatively charged electrons are located in orbits or energy levels around the nucleus.

Sub-atomic Particles Nucleus- The center of an atom. Made up of protons and neutrons. Proton- A sub-atomic particle in the nucleus of an atom. Protons have a positive electrical charge (+) and a mass of 1 atomic mass unit (amu).

Sub-atomic Particles Neutron- A sub-atomic particle in the nucleus of an atom. Neutrons are neutral, meaning that they have no charge, and a mass of 1 amu. Electron- A sub-atomic particle orbiting outside the nucleus of an atom. Electrons have a negative electrical charge and no mass. Atoms in their most stable state have an equal number of protons, neutrons and electrons.

MassChargeLocation Electrons~0 Orbits in shells around nucleus Protons1amu+1Nucleus Neutrons1amuNucleus Sub-atomic Particles

Atomic Number The number of protons in the nucleus of an atom.

Atomic Mass The number of protons and neutrons in the nucleus of an atom.

Valence Electron An electron in the outermost energy level of an atom.

Which Element? (2,8,6) Atoms are stable with 8 valence electrons

Ion An atom or group of atoms that has lost or gained electrons and is left with a net electric charge.

Chemical Bonding The attractive force that holds atoms together in molecules and compounds.

Ionic Bond A chemical bond in which electrons are exchanged between atoms. Ex: Li + F − Ex: Li + F −

Crystal Lattice An orderly, three dimensional structure produced by ions in an ionic compound.

Covalent Bond A chemical bond in which electrons are shared between atoms. Ex: O 2 Ex: O 2

Molecule A neutral group of atoms that are joined together by one or more covalent bonds.

Polar Covalent Bond A covalent bond in which the electrons are not shared equally. Ex: H 2 O Ex: H 2 O

Water Molecule

Polarity

Non-polar Covalent Bond A covalent bond in which the electrons are shared equally. Ex: O 2 Ex: O 2

Metallic Bond The attraction between a positive ion and the “sea of electrons” that surrounds it.