Chemistry Unit 2

How different substances combine with each other to make new ones

Mass is neither created nor destroyed during ordinary chemistry reaction or physical changes

A chemical compund contains the same elements in exactly the same proportions by mass regardless of the sample or source of the compound

If two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the 1st element is always a ratio of small whole numbers

• 1. All matter is made of atoms
• 2. Atoms of an elemennt are identical in size, mass, and physical properties, but atoms of different elements differ
• 3. Atoms cannot be subdivided, created, or destroyed
• 4. Atoms of different elements combine in simple whole numbers ratios to form chemical compounds
• 5. In chemical reactions, atoms are combinded, seperated, or rearranged

• 2. (Atoms of an element are identical in size, mass, and physical properties, but atoms of different elements differ)- atoms are divisable into even smaller particals
• 3. (Atoms cannot be subdivided, created, or destroyed)- A given element can have atoms with different masses

Smallest partical of an element

Small region at the center of an atom

Positively charged partical

Neutral

Negatice charge surrounding nucleus

Protons, neutrons, ands electrons

protons and neutrons

# of protons = # of electrons

Atoms of the same element have different masses (different # of neutrons)

# of protons = # of neutrons

proton

neutron

electron

atomic number

based on mass of carbon