chapter 1

Mass is the AMOUNT of matter in an object — it tells you how much “stuff” is there. Measured in grams (or kilograms)

Matter is anything that has mass and takes up space — it’s the “stuff” itself, which has mass.

atomic mass. basically protons + neutrons, as electrons basiacally weigh nothing.

Protons (+) and electrons (-) are attracted to each other because opposite charges attract

hydrogen, oxygen, nitrogen, phosporus, carbon, sulfur. (chonps)

how many protons in atoms nucleus

protons + neutron

Look at the group/family (columns) group 1 has 1, group 2 has 2, ect

Look at the period/row the element is in. Period 1 → 1 shellq Period 2 → 2 shells, etc.

An atom with a CHARGE because it has gained or lost electrons.

An atom with the same number of protons but a different number of neutrons → changes its MASS

average mass of all isotopes of that element

Alpha (α) radiation – 2 protons + 2 neutrons (helium nucleus) Beta (β) radiation – an electron or positron emitted from the nucleus Gamma (γ) radiation – high-energy electromagnetic waves (no particles, just energy) Alpha: heavy, slow, can’t penetrate skin Beta: lighter, faster, can penetrate skin a little Gamma: very penetrating, requires thick lead or concrete to block

Molecules are two or more atoms chemically bonded together. ex, h2o or o2- BONDED ATOMS

electrons

a region around the nucleus where an electron is most likely to be found. Think of it like a “parking spot” for an electron.

a group of orbitals at the same energy level around the nucleus. Think of it like a “parking lot” that holds one or more orbitals.

atoms share electrons. H₂O (oxygen shares electrons with hydrogen)

atoms transfer electrons. NaCl (sodium gives up an electron to chlorine)

basic building block of all matter

the top number (the group) vertical row!

the side numbers (the period) horizontal row!

Buffers are chemicals that resist changes in pH.

Law of Mass Action: The rate and direction of a chemical reaction depend on the concentrations of reactants and products. Basically, a reaction will shift forward or backward to reach equilibrium depending on how much of each substance is present. Example: A + B ⇌ C + D If there’s a lot of A and B, the reaction moves forward → more C and D form. If there’s a lot of C and D, the reaction moves backward → more A and B form.