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Mass, indivisible.

Dalton incorporated the law of conservation of _____ into his atomic theory by asserting that atoms are _____.


If each atom of element D has 3 masses and each atom of element E has 5
mass units, a molecule composed of one atom each of D and E has _____ mass units.

Multiple Proportions

In oxides of nitrogen atoms combine in small whole-number ratios. This evidence supports the law of _____

The Law of Multiple Proportions

states that two or more compounds different compounds of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers

equal to

According to the law of conservation of mass, when sodium, hydrogen, and
oxygen react to form a compound, the mass of the compound is
________ (equal to, greater than) the sum of the masses of the
individual element.

John Dalton

Who conceived the principles of the atomic theory?

identical, mass

According to Dalton's atomic theory, atoms of each element are __________ in size, _____ and other properties.


Atoms of the same element may have _____ masses according to modern atomic theory.

Atoms can be subdivided

Which concept of Dalton's atomic theory has been changed?

A negatively charged electrode

What is a cathode?


If an electrical current passes through a glass tube, it causes the surface of
the tube directly across from the cathode to glow. The reason is because the particles of the bean were _______ charged.


Experiments with cathode rays led to the discovery of

Thompson, small

After measuring the ratio of the charge of a cathode-ray particle to its mass, _______ concluded that the particles had a very ________ mass.

negatively charged electrons

Because any element used in the cathode produced _______scientists concluded that all atoms contained electrons.

Rutherford, gold, through, empty, densely, positive

_______ experiments identified the nucleus of that atom. In his experiments, alpha particles were used to bombard thin ______ foil. Most of the particles passed _______ the foil. Because most of the particles passed through, Rutherford concluded that atoms were mostly _______ space. Because a few alpha particles bounced back from the foil, he concluded that they were repelled by _______packed regions of _______ charge.

neutron, mass, positive

A _______has the same _______as a proton, but with no _______ charge.

positively charged, contains all the mass of the atom, densely packed

What are the characteristics of the nucleus of an atom?

protons, electrons, equal

An atom is electrically neutral because the numbers of _________ and _________ are _________

Electron cloud

Most of the volume of an atom is occupied by the _________.

atoms, masses

Isotopes are _________ of the same element that have different _________.


The most common form of hydrogen has no _________.


The atomic number of oxygen, 8, indicates that there are 8
_________ in the nucleus of the an oxygen's atom.


An aluminum isotope consists of 13 protons, 13 electrons, and 14
neutrons. It has a mass number of _________.


The number of atoms in 1 mol of carbon is _________


The atomic number of neon is 10. The atomic number of calcium is 20.
Compared with a mole of neon, a mole of calcium contains an
________ number of atoms.


What is the mass of 1 mol of chromium


atoms of the same element that have different masses


Atoms of different elements have different numbers of ______.


Positively charged sub-atomic particle


Negatively charged sub-atomic particle


Sub-atomic particle with no charge.

Atomic Number

The number of protons found in each atom of an element is known as that element's ______.

Mass Number

Total number of protons and neutrons that make up the nucleus of an isotope.

17 protons, 17 electrons, 20 neutrons

How many protons, electrons, and neutrons are there in Chlorine(Cl) -37? (In that order)

6 protons, 6 electrons, 6 neutrons

How many protons, electrons, and neutrons are there in Carbon(C) -12? (In that order)

24 protons, 24 electrons, 34 neutrons

How many protons, electrons, and neutrons are there in Chromium(Cr) -58? (In that order)

By their mass, (due to) the number of neutrons

How can you tell isotopes apart?

Mass Number

What does the number next to isotopes signify? (Ex. Nitrogen-15)


The central part of an atom containing the protons and neutrons.

Atomic Mass

The average mass of the atoms in an element.


3.00 mol NH3 to grams of NH3


8.00g NaOH to molecules of NaOH


9.02 mol H2O to molecules of H2O


0.2000 mol SO3 to grams of SO3

0.0577 mol

5.657g H2SO4 to moles of H2SO4

earth, water

The ancient Greeks believed that matter is made up of four basic elements: _____, air, fire, and ______.

John Dalton

man who proposed the modern atomic theory.

constant composition
definite proportions.
Either is acceptable, mark as correct.

The law of ________ says that the composition of a compound is always the same.


In science, a prediction is known as a ________.

Electrons, J. J. Thompson

________, tiny, negatively charge particles were discovered by ________.


The number of protons in an atom is always equal to the number of ________.


isotopes differ from one another in their________.


Gold foil experiment


Discovered the nucleus

Electron Cloud

The largest portion of an atom is taken up by the ________.


Symbol for the atomic mass unit is ___.

10, 20, 10

Give the atomic number, mass number, number of electrons

238, 92, 92

Atomic Number = 92
Number of neutrons = 146
Give the mass number, number of protons, number of electrons

13, 27, 13

Number of neutrons = 14
Number of electrons = 13
Give the atomic number, mass number, number of protons


400 B.C. ________ though matter could not be divided indefinitely.


Dalton: All matter is made of ________.

John Dalton

His ideas account for the law of conservation of mass, and the law of constant composition.

Cathode Rays

Materials, when rubbed, can develop a charge difference. This electricity is known as ________when passed through an evacuated tube.

John Dalton

"Billiard Ball" Model
-Atoms are solid and indivisible


"Plum Pudding" Model
-Negative electrons in a positive framework


His model states that atoms are mostly empty space. Negative electrons orbit a positive nucleus.


Shot alpha particles at gold foil. most particles passed through, showing that atoms are mostly empty space.
Thus, this scientist could conclude that the nucleus holds most of the atom's mass.


Scientist who believed:
-Electrons orbit the nucleus in "shells"
-Electrons can be bumped up to a higher shell if hit by another electron or a photon of light.

electrons, atomic (number)

#protons = # of ________ = ________ number


# of ________ = mass number - atomic number


Radioactivity is caused by a large gap between ________ and protons.
(As in Uranium(U) 92p+ 92e- 146n)

Nuclear Forces

Short-range neutron-neutron, proton-proton, and neutron-proton forces that hold nuclear particles together are called ________.


There are no example problems here because I didn't do the practice worksheets and don't have the correct answers.
(answer: type OK)


Oil Drop Experiment. Found the charge of an electron.

divisible, masses

What was incorrect about Dalton's theory:
-Atoms are ________ into smaller particles.
-A given element can have atoms with different ________.

Law of conservation of mass

atoms are neither created nor destroyed.(Law)

Law of constant composition
Law of definite proportions.
Either is acceptable, mark as correct.

elements combine in fixed ratios.(Law)

Law of multiple proportions

If two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers. (Law)

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