| A | B |
|---|
| What are the basic units of matter? | atoms |
| How many different kinds of atoms are in nature? | over 100(each called elements) |
| Describe the make-up of an atom. | a nucleus surrounded by a cloud of electrons at different energy levels |
| What does an atom's nucleus contain? | protons and neutrons |
| How many protons do atoms of the same element have? | the same number of protons |
| What is different about isotopes of the same element? | different number of neutrons(but same number of protons) |
| What is the mass number? | total number of protons and neutrons in an atom |
| What is an element? | a substance made of just one kind of atom |
| How are elements represented? | with a one or two letter chemical symbol |
| What is a compound? | a substance made of two or more elements chemically combined |
| The properties of a compound differ from the properties of the ________ that make it up. | elements |
| Some compounds exist as ________ others are _________ ________. | molecules; ionic compounds |
| The makeup of a compound can be described by a _______ ________. | chemical formula |
| What is a mixture? | formed when two or more different substances are mixed but not chemically combined |
| Each part of a ____________ keeps its original properties and can be separated. | mixture |
| Mixtures can be ___________ or __________. | homogeneous; heterogeneous |
| Dalton's model | developed in early 1800's, all matter composed of atoms, atoms solid & invisible spheres, atoms of same element are alike, atoms of different elements have different masses, atoms of different elements can join to form compounds |
| Thomson's model | developed in late 1800's, discovered electrons, atoms are not indivisible there are positive and negative pieces, atoms are electrically neutral-charges must equal and balance out the positive charges, positive and negative stuck together, "plum pudding" model |
| Rutherford's model | developed in early 1900's, used "Gold-Foil experiment" showed that atoms were mostly empty space and nucleus was small speck in middle, called "nuclear model", scientist were very skeptical, shouldn't positive and negative charges attract |
| Bohr's model | developed in 1913, thought that electrons existed in shells or energy levels around the nucleus, electrons move around the nucleus much like planets around sun, called "Planetary Model" |
| Electron Cloud model | current model, electrons exist in areas(clouds) around the nucleus, can describe location of electron but cannot say how electrons move from one place to another, don't believe electrons orbit, energy levels contain more electrons the farther they are from the nucleus |
| What is the atomic number? | number of protons in an atom, determines the name of element(it also equals the number of electrons) |
