Composition of matter
all of the atoms in a sample of matter have the same identity
what is an element?
any characteristic of a material that you can observe without changing the substances that make up the material
what is a physical property?
positively charged particles found inside a nucleus
what are protons?
atoms of the same element that have different numbers of neutrons
what are isotopes?
the periodic arrangement of elements
what is the periodic table?
either an element or a compound
what is a substance?
any change in the size, shape, or state of matter of a substance
what is a physical change?
negatively charged particles that surround a nucleus
what are electrons?
the sum of the number of protons and neutrons in the nucleus of an atom
what is a mass number?
vertical columns in the periodic table
what are groups?
made from atoms of two or more elements
what is a compound?
a change in one substance in a material to a different substance
what is a chemical change?
particles in the nucleus that have a neutral charge
what are neutrons?
letters or pairs of letters used to write the abbreviated name of an element
what are chemical symbols?
solids at room temperature, shiny, and good conductors of heat
what are metals?
a heterogeneous mixture in which visible particles settle
what is a suspension?
a characteristic of a substance that indicates whether it can undergo certain chemical changes
what is a chemical property?
the number of protons found in the nucleus of an atom
what is an atomic number?
this model is used to describe the location of an electron
what is the electron cloud?
elements to the right of the "stair step line"
a heterogeneous mixture that never settles
this states that matter can neither be created nor destroyed
what is the law of conservation of mass?
the positively charged center of an atom
what is the nucleus?
the average mass of the mixture of an element's isotopes
what is an average atomic mass?
this scientist designed the first periodic table
who is Mendeleev?