Science chapter 3
atomic mass unit (amu)
1/12 the mass of a carbon-12 atom
subatomic
Dalton theorized that atoms are indivisible, but the discovery of _____ particles change this theory
small whole-number
Dalton's atomic theory included the idea that the atoms of different elements can chemically combine in _____ ratios
negative, protons, neutrons
scientists now know that atoms are made of elections, which have a _____ charge; _____, which have a positive charge; and _____, which are neutral
cathode ray
stream of electrons produced at the negative electrode of a tube containing gas at low pressure
atomic mass
the _____ of an element is the weighted average of the masses of the isotopes of that element
always
the atomic number of an atom is the total number of protons in an atom of that element
always
the charge on all protons is the same
period
a horizontal row of the periodic table
proton
a neutron has no charge, but its mass is almost the same as that of a _____
group
a vertical column of elements in the periodic table
never
according to Dalton's atomic theory, atoms are composed of protons, electrons & neutrons
chemical reaction
an atom is the smallest particles of an element that retains its identity in a _____
sometimes
an atom of nitrogen has 7 protons & 7 neutrons
sometimes
atoms combined in one-to-one rations to form compounds
different
atoms of any one element are _____ from those of any other element
compounds
atoms of different elements can form _____ by combining in whole-number ratios
sometimes
atoms of elements are electrically neutral
always
atoms of one element are different from atoms of other elements
never
atoms of one element change into atoms of another element during chemical reactions
neutrons
atoms of the same element are identical in most respects, but they can differ in the number of _____ in the nucleus
isotopes
atoms that have the same number of protons but different mass numbers are called _____
electrons
because atoms are electrically neutral, the number of protons & _____ in an atom are equal
separated, joined, rearranged
chemical reactions occurs when atoms are _____, _____, or _____
1
each of the three known isotopes of hydrogen has _____ proton(s) in the nucleus
atoms
elements are composed of tiny particles called _____
mass number
equals the number of neutrons plus the number of protons in an atom
electrons
in contrast, the negatively charged _____ occupy most of the volume of the atom
mass
isotopes of an element have different numbers of neutrons. they also have different _____ numbers
1
it has a mass number of _____ and is called hydrogen-1
Rutherford
it was _____ who discovered the nucleus of the atom
atomic number
number of protons in the nucleus of an atom of an element
always
relative atomic masses are expressed in amus
never
the atomic number of an element is the sum of the protons & electrons in an atom of that element
atomic numbers
the elements in the period table are listed in order of increasing _____
nucleus
the latter two particles are found in the _____ of the atom
30
the mass number of an element with 14 electrons & 16 neutrons is _____
never
the mass of an election is equal to the mass of a neutron
0
the most common hydrogen isotope has _____ neutrons
positive
the nucleus, which has a _____ charge, occupies a very small volume of the atom
proton
the number of _____ in the nucleus of an atom is the atomic number of that element
always
the number of neutrons in the nucleus can be calculated by subtracting the atomic number from the mass number
atomic
the number of protons in an atom is called its _____ number
protons
the total number of _____ and neutrons in an atom is the mass number
156
the total number of subatomic particle in an atom of silver-109 (atomic number 47) is _____
8
there are 10 neutrons and _____ electrons in an atom of oxygen-18
protons & neutrons
what subatomic particles are found in the nucleus of an atom?
electrons & protons
which subatomic particles are charged?
