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