Chp 4 Worksheets
an electrode with a negative charge
cathode
a glowing beam traveling between charged electrodes
cathode ray
atoms of different elements can form _____ by combining in whole-number ratios.
compounds
(T or F) An alpha particle has a double positive charge because it is a helium atom that has lost two electrons
true
About how many atoms of copper when placed side by side would form a line 1 cm long?
100,000,000
what is the mass number of helium atom that has two protons and two neutrons
4
How many neutrons does a beryllium atom with four protons and a mass number of nine have
5
atoms of one element are different from atoms of other elements
AT
The modern process of discovery about atoms began with the theories of an English school teacher named _______
Dalton (John Dalton)
Greek philosopher who was among the first to suggest the existence of atoms
Democritus
English chemist and schoolteacher who formulated a theory to describe the structure and chemical reactivity of matter in terms of atoms
John Dalton
Atoms of one element change into atoms of another element during chemical reactions (AT,ST,NT)
NT
Atoms combine in one-to-one ratios to form compounds
ST
Why is the atomic mass unit (amu), rather than the gram, usually used to express atomic mass?
The value of even the largest atom is incredibly small
How is the atomic theory that is accepted today different from Dalton's atomic theory?
They can be broken down into even smaller pieces
List 2 reasons why the ideas of Democritus were not useful in a scientific sense
They did not explain chemical behavior and lacked experimental support
Suppose you could grind a sample of the element copper into smaller and smaller particles. The smallest particle that could no longer be divided, yet still has the properties of copper, is
an atom
an electrode with a positive charge
anode
The smallest particle of an element that retains its identity in chemical reaction
atom
Democritus, who lived in Greece during the fourth century B.C., suggested that matter is made up of tiny particles that cannot be divided. He called these particles
atoms
elements are composed of tiny particles called
atoms
atoms of any one element are ____ from those of any other element
different
a negatively charged particle
electron
Neon-20 and neon-22 are called
isotopes
the total number of protons and neutrons in the nucleus of an atom
mass number
How do atoms of neon-20 and neon-22 differ?
neon-22 has 2 more neutrons than neon-20
What charge does a neutron carry?
neutral
The positively charged subatomic particle that remains when a hydrogen atom loses an electron is called a
proton
an instrument used to generate images of individual atoms
scanning tunneling microscope
Chemical reactions occur when atoms are _____
separated
