8th grade chemistry basics ig

u got this i hate this (chemistry)

matter

Anything that has mass and takes up space

elements

simplest pure substance; cannot be broken into simpler units by chemical reactions.

compound

A substance made up of atoms of two or more different elements combined chemically to form a specific ratio

Mixture

A combination of two or more substances that are not chemically combined, but are in the same place

atom

Smallest particle of an element

scientific theory

a well-tested idea that explains and connects various observations

model

physical mental visual or other rep of idea to help people understand what they cant observe

atomic theory

1. Each element is composed of tiny, indestructible particles called atoms.

2. All atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements.

3. Atoms combine in simple, whole-number ratios to form compounds.

4. Atoms of one element cannot change into atoms of another element. In a chemical reaction, atoms only change the way that they are bound together with other atoms.

Electron

A subatomic particle that has a negative charge

protons

Positively charged particles

energy level

the specific amount of energy an electron has

valence electrons

electrons with the highest energy level and are held the most loosely

electron dot diagram

A model of an atom in which each dot represents a valence electron (symbol of element surrounded by dots)

chemical bond

the force that holds two atoms together as result of rearranging electrons between them

periodic table

system used worldwide for organizing elements into categories

symbol

1 or 2 letters that rep an element

period

A row on the periodic table

group/family

a vertical column of elements in the periodic table

noble gases

Group 18 with 8 valence electron, don't react easily

halogens

Contains nonmetals, 7 valence electrons in it's outermost energy level. Very reactive (group 17)

alkali metals

Group 1, 1 valence electron, reactive

alkaline earth metals

Group 2

ion

An atom or group of atoms that has an electric charge.

polyatomic ion

an ion made of two or more atoms

ionic bond

A chemical bond resulting from the attraction between oppositely charged ions (positive and negative).

ionic compounds

a compound composed of positive and negative ions

subscript

A number written slightly below and to the right of a chemical symbol that shows ration of elements in compound

crystal

An orderly, three-dimensional pattern of ions or atoms in a solid, pattern remains the same and repeats over and over again

electrical current

a flow of charged particles from one point to another

covalent bond

A chemical bond formed when two atoms share electrons

molecule

two or more atoms held together by covalent bonds (neutral)

double bond

A covalent bond in which two pairs of electrons are shared between two atoms

triple bond

a covalent bond in which two atoms share three pairs of electrons

molecular compound

a compound that is composed of molecules

metallic bond

an attraction between a positive metal ion and the electrons surrounding it

alloy

A mixture of two or more metals (has properties of metal)

ductile

A term used to describe a material that can be pulled out into a long wire

malleable

rolled or beaten into thin sheets (like aluminum)

luster

The way a mineral reflects light

who created the idea that matter is formed of small parts that can't be divided

democritus

Who created the atomic theory?

John Dalton

who found that atoms contain negatively charged particles (negative charges scattered throughout ball of positive charge)

jj thomson

who found that the atoms positive charge is clustered in nucleus

ernest rutherford

who found that electrons could have only specific amts of energy (orbit around nucleus)

niels bohr

who discovered neutrons

James Chadwick

what does # of valence electrons determine

the chemical properties of an element (including how they bond with another atom)

atoms usually react in a way that makes them more what?

stable

t/f molecular compounds can conduct electricity well

false, they can not

what does heat cause particles of matter to do?

move faster therefore allowing energy (heat) to transfer to cooler parts and heating them up.

t/f metals conduct electricity easily (why)

true, bc electrons in a metal can move freely among atoms

chemical formula

Symbols that show the elements in a compound and the ratio of atoms

why are elements called the building blocks of matter

all matter is composed of one element or a combo of 2 or more

as the atomic number increases (# of protons) what happens to electrons and what happens to the properties across a period?

the number also increases, it changes in a regular way

what happens when an atom loses an electron?

it becomes a positive ion

what happens when an atom gains an electron

it gains a negative charge and becomes a negative ion

How do ionic bonds form?

as a result of the attraction between positive and negative ions

how do ions come together in ionic compounds, what reflects this balance?

in a way that balances out the charges, chemical formula

in ionic compound which name comes first and which follows

positive ion first, negative second (MgO) magnesium is positive, oxygen is negative

If no subscript is written, what is understood

1, there is a 1 to 1 ratio (NaCl: 1 to 1 ratio of sodium to chloride ions)

ions are hard, brittle _______ that have high ______

crystals, melting points

when ________ in water or _________ crystals conduct____________

dissolved in water or melted crystals conduct electricity

the force that holds atoms together in a covalent bond is the what?

attraction of each atoms nucleus for the shared pair of electrons

Compared to ionic compounds, molecular compounds generally have...

lower melting point and boiling points

they do not conduct electricity when dissolved in water

atoms of some elements pull more strongly on shared electrons than do atoms of other elements, as result...

electrons are pulled toward one atom causing the bonded atoms to have slight electrical charges.

polar bond

a covalent bond in which electrons are shared unequally

nonpolar bond

a covalent bond in which electrons are shared equally

a metal consists of positively charged metal ions embedded in what?

"sea" of valence electrons

"sea of electrons" model of solid metals explains what?

their ability to conduct heat and electricity, the ease with which they can be made to change shape, and their luster.