UNIT 2 – Matter and Atoms

What is Chemistry?? Chemistry: the study of non-living matter, and the changes non-living matter undergoes. Matter: anything that has mass and takes up space.

All matter in the world is either a pure subtance or mixture.

Pure sub-stance that is made up of only one type of atom Element - Pure sub-stance that is made up of only one type of atom Pure Substance- Matter that always has exactly the same composition – the properties are fixed Compound – Substance that is made of more than one type of atom

(Pure) Substance- Element – Compound – Matter that always has exactly the same composition – the properties are fixed Element – A substance that cannot be broken down into simpler substances Compound – A substance that can be broken down into those simpler substances Properties differ from those of the substances from which it is made (water – H and O) Contains only one type of atom Ex: aluminum, carbon oxygen, nitrogen, mercury Always contains two or more elements joined in a fixed proportion (H20)

Properties differ from those of the substances from which it is made So let's think about it... Water is H O 2 At room temperature... Hydrogen is a gas Oxygen is a gas water is a liquid

Mixtures – properties can vary because the composition is NOT fixed Individual properties: tend to retain some properties of their individual substances (ex: Salsa) Homogeneous Mixtures – parts are so evenly distributed that it is difficult to distinguish one substance from another. (ex: Kool-Aid) Heterogeneous Mixtures– parts are noticeably different from one another (ex: sand)

Homo - same Hetero - different

Mixtures Continued Solutions A mixture in which you cannot see the different parts (homogenous) Has the smallest particles Do not separate into layers over time Light passes through them, particles don’t scatter light (too small) Cannot be separated by a filter Example: sugar in hot water; windshield wiper fluid; Kool-aid

Mixtures Continued Colloids “Cloudy” mixture Medium-sized particles Do not separate into layers Cannot use a filter to separate the parts Particles scatter light Examples: milk, fog, Jello

Mixtures Continued Suspensions A heterogenous mixture-you can see the different parts. Large particles. Will separate into layers over time Can use a filter to separate parts Particles scatter light Examples: Muddy water; Italian salad dressing, salsa.

Suspension Colloid

Solution Contact Lens Cleaner Colloid Milk Suspension

Structure of the atom Electron, (-) charge Proton, (+) charge (smallest part of an element) Electron, (-) charge - Proton, (+) charge + Neutron, (0) charge - - + These are called subatomic particles… + + - This is called the Nucleus

ELECTRONS NEGATIVE CHARGE (-1) Orbit the nucleus Light in mass (1/1836 of a proton)

PROTONS POSITIVE CHARGE (+1) Found in the nucleus (center) of an atom Heavy in mass (1 atomic mass unit, 1amu)

NEUTRONS NEUTRAL (0) CHARGE Found in the nucleus Heavy in mass (1 atomic mass unit,1amu)

Number ofprotons or electrons. All normal atoms are neutral. READING ELEMENTS ON THE PERIODIC TABLE Atomic Number C 6 12.01 Number ofprotons or electrons. Unique to each element. All normal atoms are neutral.

C 6 12.01 Mass Number (rounded to whole number) READING ELEMENTS ON THE PERIODIC TABLE C 6 12.01 Mass Number (rounded to whole number) Number of Neutrons Number of Protons

The AVERAGE mass number of all the different isotopes of an element. READING ELEMENTS ON THE PERIODIC TABLE C 6 12.01 Atomic Mass The AVERAGE mass number of all the different isotopes of an element.

Electron Configuration The arrangement of electrons of an atom.

Electrons are arranged in areas that surround the nucleus Electrons are arranged in areas that surround the nucleus. These areas are called energy levels.

The first energy level can hold 2 electrons. The second energy level can hold 8 electrons. The third energy level (and all others) can hold 8 electrons.

Atoms always fill the energy levels from the inside out. Once the energy level closest to the nucleus has 2 electrons, the next energy level begins to be filled.

Ions Atoms want 2 or 8 electrons in valence shell Atoms having more or less electrons than they normally do. Atoms want 2 or 8 electrons in valence shell