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Chapter 17-study

study guide for chapter 17

QuestionAnswer
What is the building blocks of most matter? atoms
atoms make up everything in the universe that we see, ?, taste, ? and smell. feel, hear
what is the smallest particles of an element that can be identified with that element? atoms
a substance made up of only one kind of atom. element
? percent of the material on earth is formed from only a dozen of the elements (most of them are rare) 99 percent
5 most common elements that make up living things. (most common) oxygen, carbon, hydrogen, nitrogen, calcium
What us chemical symbol? letter or letters that represent an element.
Lightest element? Hydrogen
Hydrogen makes up what percent of all the atoms in the universe? 90 percent
what element is the second lightest element? Helium
makes up what percent of atoms in the universe? (although its rare on earth) 10 percent
How and where are heavier elements formed? Fusion reactions inside stars
When are elements heavier than iron formed? during super-novas
How are the heaviest elements formed? when pairs of neutron stars collide.
almost all the atoms on earth are the remains of what? stars
what percent of matter is composed of dark unseen matter? 23 percent
atoms are slowest in? solids
atoms are faster in? liquids
atoms are fastes in? gases
How long does it take for one of you exhaled breaths to becom evenly mixed in the atmosphere? about six years
atoms are much older that the ? they compose. material
who said matter was made of atoms because of studying chemical reactions? John Dalton
What is Browanian motion? constant jiggling of particles just large enough to be seen.
? is smallest particle of a substance consisting of two or more atoms that bond together by sharing electrons. Molecule
Molecules can be made up of atoms of the ? element of of ? element. same, different
What is the most common molecule? water-H2O
True or false: Not all matter is made of molecules. True
Metals are... rows of individual atoms
True or False: Molecules can't be detected by all of our senses. False, they can be detected by all of our senses.
what is a compound that is made of atoms of different elements comined in a fixed proportion? Compound
What tells the proportions of each kind of atom? Chemical Formula
True or false: a compund may or may not be made of molecules. True
Compounds have properties ? from those of the elements of which they are made. different
what are two gases? Hydrogen and oxygen
True or false: atoms are mostly empty space. True
Where is the mass of an atom primarily concentrated? Nucleus
What is the central region of the atom? Nucleus
What prevents close packing of atomic nuclei? Electrical repulsion.
When nuclei of two or more atoms are squashed together into contact this is called? Nuclear fusion
What are the building blocks of the nucleus? nucleons
Neutrons are electrically what? neutral
Protons electric charge is? positive
Total number of nucleons in the nucleons of the atom. Atomic mass number
How do you get the mass number? protons plus neutrons (really subtracting)
True or false: atoms of various elements differ in the number of protons. true
what are atoms of the same element having different numbers of neutrons? isotopes
what are the two types of electric charges? positive protons, negative electrons
Like charges... unlike charges... repel attract
protons repel ? but attract electrons protons
electrons repel electrons but attract ? protons
how are protons held together in the nucleus? by a strong nuclear force
what do electrons orbit? nucleus
True or false: the number of negatively charged electrons must equal the number of postively charged protons. True
When the number of electrons is more or less than the number of protons in the atom, the atom is no longer neutral and has a net charge. It is now called? an ion
what is the shell model of an atom? a model in which the electrons of an atom are pictured as grouped in concentric shells around the nucleus.
how many different shells have its own capacity? seven
the first shell can hold? 2 electrons
the second shell can hold? 8 electrons
the outer shell cant hold more than? 8 electrons
what dictates the atom's physical and chemical properties? the arrangement of electrons
What forms a chemical bond between elements? the sharing or transferring of electrons
how do covalent bonds form? when two atoms share electrons
How do ionic bonds form? when electrons are transferred between atoms
what are the four phases of matter? solid, liguid, gas
what matter consists of positive ions and free electrons? plasma
true or false: all substances can be transformed from one phase to another by heating. True
Created by: cwillett