chemistry

what is a mixture

when 2 or more substances are combined

what determines reactivity

the number of valence electrons

what are the horizontal rows on the periodic table called

periods

what theory did aristotle create and explain

theory of transmutation. can turn materials into other materials ex. lead to gold

what are the vertical columns on the periodic table called

groups/families

what is chemistry

the study of matter

what is matter

anything that has mass

what is the difference between element and compound molecules

element molecules only have 1 type of atom and compound molecules have multiple types of atoms

what information can be found on the periodic table

atomic mass, number, symbol, reactivity and chemical properties

what determines the identity of an element

the number of protons in the nucleus

what happened if an atom gains or loses electrons

becomes positively or negatively charged

why are noble gases inactive/stable

they have a full valence shell, aren’t trying to gain or lose electrons

describe a bohr diagram

a small circle with the number of p and n, surrounded by shells with the correct number of electrons in order 2,8,8

why are atoms electrically neutral

the same number of protons and electrons

what is an isotope

different versions of the same element with the same number of protons but a different number of neutrons

what are the signs of a chemical change

bubbles, precipitation, colour change, volume change, temperature change, smell

what is a compound formula

a combination of chemical symbols that shows how many and what elements are in the compound

what is a molecule

the smallest unit of a compound

what is a compound

a pure substance made of identical molecules

what is an atom

the smallest unit if an element made of protons neutrons and electrons

what are metaloids

found on the staircase and have both metal and non metal properties

what are nonmetals

15% of elements, far right side, not conductive, not shiny, brittle. carbon, iodine, sulfur

what are metals

75% if elements, left side, shiny, conductive, ductile. copper, lead, nickel

what is group 18

noble gases. contains He,Ne,Ar. stable. have a full valence shell

what is group 17

halogens. very reactive with almost everything. contains F,Cl,Br. have 7 valence electrons

what is group 16.

chalcogens. Contains O,S,Se. quite reactive. 6 valence electrons

what is group 3

Alkaline earth metals. contains Be,Ca,Mg. fairly reactive. similar to alkali metals. 2 valence electrons

what is group 2

alkali metals. Contains Li,Na,K. have 1 valence electron. react vigorously

what is group 1

hydrogen extremely reactive

what are periodic table periods

horizontal rows labelled 1-7 based on my of electron shells

what are groups/families

vertical rows labeled 1-18 based on number of valence electrons.have similar chemical properties

what are valence electrons

elections in the outermost shell of an atom

what are the first 18 elements

H HE LI BE B C N O F NE NA MG AL SI P S CL AR

what is atomic mass

number of protons - number of neutrons

what is atomic number

the number of protons in the nucleus

what is a chemical change and give an example

changes into a new substance with different properties a new substance is formed. car rusting, food digesting, egg cooking; wood burning

what is a physical change and give an example

only changes the appearance, state or form of the substance and is typically reversible. dissolving sugar in water or cutting paper

what is a chemical property and give 3 examples

describes the behaviour of a substance. combustibility, reactivity, toxicity, flammability

what is a quantitative physical property and give examples

physical properties that can be measured. conductivity, melting and boiling point, viscosity, density, solubility

what are qualitive physical properties and give examples

physical properties that can be observed

state, colour, lustre, malleability, texture

what’s the the charge, symbol, and location of the 3 subatomic particles

electrons: e-, negative, electron shells

protons: p+, positive, in the nucleus

neutrons: n•, neutral, in the nucleus