Properties of Atoms, Molecules, & Bonds

matter

any substance that takes up space and has mass

atoms

smallest unit of matter and form all chemical substances

elements

unique forms of matter with specific chemical and physical properties that cannot be broken down into smaller substances

4 elements common to all living organisms

oxygen, carbon, hydrogen, nitrogen (96% of life)

trace elements

only required in very small quantities

compounds

form when two or more elements are bonded together. may have different properties than those of it’s individual elements (NaCl)

two regions of the atom are

nucleus region and orbital region

nucleus region

atom’s center and contain protons and neutrons

orbital region

holds atom’s electrons in orbit around the nucleus.

why are hydrogen atoms an exception to the octet rule/orbital region?

they are made of 1 proton and 1 electron with no neurtrons

1.67×10^-24

one atomic unit or one dalton

mass number

number of protons plus the number of neutrons

contributes to mass

protons and neutrons

contributes to charge

electrons and protons

repulsive force

negative charges repel each other and can’t pass through each other

atomic number

number of protons. different for each element, so the number of protons is what distinguishes one element from another

isotopes

different versions of the same element that have the same number of protons but a different number of neutrons

atomic mass

takes into account all of an atom’s isotopes and their relative abundances (how many atoms of that isotope exist)

average mass of protons and neutrons, including isotopes

periodic table

groups elements based off their chemical properties

shells

region of space surrounding the nucleus where you find electrons

orbitals

specific regions within a shell

consistent order to fill shells with electrons:

innermost to outermost. follows 2,8,8 rule

valence shell

outermost electron orbital of an atom

octet rule

atom is most stable energetically when they have a full valence shell (8 electrons and 2 for hydrogen)

inert or noble gases

elements that have full valence shells and are highly stable (form no bonds because of this)

molecule

chemical structure resulting from 2 or more atoms that have chemically bonded

molecular formula

contains chemical symbols of the elements in the molecule

chemical reaction

when two or more atoms bond to form molecules or when bonded atoms break apart

ionic bonds

electrons are transferred forming ions that are attracted to each other taking OR giving away electrons (for because of electrons and shells) (form when cation binds to anion by electrostatic attraction)

ion

an atom that is more stable once it has gained or lost an electron

cation

positive ions that form by losing electrons

anion

negative ions that form by gaining electrons

ionic compounds

salts

covalent bond

electrons are shared to fill valence shells; can be polar covalent or nonpolar covalent
atoms SHARE 1, 2, or 3 pairs of electrons

polar covalent bond

atoms unequally share electrons and are attracted more to one nucleus than the other. (creates slightly negative or slightly positive charge)

nonpolar covalent bond

form between two atoms of the same element or between different elements that share electrons equally. (no charge difference across molecule because atoms are sharing electrons)

hydrogen bond

hydrogen atom from one polar molecule is attracted to an electro negative atom from another molecule

share, but unequally - H will be slightly positive (form because of charge)

weak bonds that form and break easily