Chemistry 10th Honors- Midterm

What is the current model of the atom?

Schrondinger

Name the Model:

-Electron Cloud Model

-Electrons are constantly in motion around the nucleus in different shaped orbitals

-Electrons have properties of waves and particles

-Nucleus contains protons and neutrons

Schrodinger

Who proposed the existence of the atom?

Democritus

Who said atoms are solid, homogeneous, indestructible, and indivisible?

Democritus

Who said atoms have different shapes and sizes?

Democritus

Who rejected the ideas of Democritus?

Aristotle

Who said empty space cannot exist?

Aristotle

Who said matter is made of earth, fire, air, and water?

Aristotle

Who said atoms are building blocks of matter?

John Dalton

Who said atoms are indivisible?

John Dalton

Who said atoms of the same element are identical?

John Dalton

Who said atoms cannot be created or destroyed, only rearranged in chemical reactions?

John Dalton

Who said atoms unite in small, whole number ratios to form compounds?

John Dalton

Who said there was a Solid sphere model (Billiard Ball)?

John Dalton

Who discovered the electron (proved Dalton’s indivisible atom idea was wrong)?

J.J. Thomson

Who proposed the plum pudding model?

J.J. Thomson

What is the Plum Pudding Model?

Model that suggests:

Negatively-charged “plums” in a positively-charged pudding

Who said most of the atom is empty space?

Ernest Rutherford

Who said atoms have a dense, positively-charged center?

Ernest Rutherford

What is the name of Ernest Rutherford’s experiment?

Gold-foil experiment

What did Rutherford do in the Gold Foil experiment?

Aimed alpha particles at gold foil

Most particles passed through,

but some bounced back

What did the Gold Foil Experiment prove?

the existence of a dense center as opposed to a positive blob with electrons stuck to it

Who worked with Rutherford?

Niels Bohr

Who kept the idea of the positive center and said electrons are in energy levels and orbit the nucleus like planets around the sun?

Niels Bohr

Who proposed the planetary model?

Niels Bohr

Who built off Bohr’s model?

James Chadwick

Who discovered the neutron?

James Chadwick

Who said the mass of a neutron = Mass of a proton

and the neutron is neutral?

James Chadwick

Put the atom scientists in order.

Democritus→Aristotle→John Dalton→J.J. Thompson→Ernest Rutherford→Niels Bohr→James Chadwick

A mass spectrum of Argon shows that it has three major isotopes, Argon-36 (0.34%), Argon-38 (0.06%), and Argon-40 (99.60%).

Which of the following best explains why the average atomic mass of Argon is 39.948 amu?

The average is closest to Argon-40 because it is found in the highest percentage.

Using correct significant figure rules, what would be the average atomic mass of two isotopes of an unknown element. One isotope is 14.00 amu and 99.6%, and the other is 15.00 amu and 0.4%.

14.0 amu

There are two isotopes of an unknown element. One has a mass of 10.01 amu and a percentage of 19.1%. The other has a mass of 11.01 amu and a percentage of 80.9%. What is the average atomic mass of this unknown element?

10.82 amu

When using the percent abundance of each isotope of an element to calculate average atomic mass, it is important to remember to...

convert it back to decimal form

What two things are needed to calculate average atomic mass?

Mass # and percent abundance

There are four major isotopes of Cerium: Cerium-136, Cerium-138, Cerium-140, and Cerium-142. One of these isotopes has an abundance of 88.4%, one 11.1%, and the remaining two are 0.2% and 0.3%.

If the average atomic mass of Cerium is 140.116 amu, which isotope is the most abundant?

Cerium-140

What is the mass number of Be with 5 neutrons?

9

The number of protons is equal to the number of ________.

electrons

What is the mass number of Ga with 41 neutrons?

72

What is the atomic number of Bromine-79?

35

What is the atomic number?

30

What is the mass number?

52

Neutral atoms have no electrical charge because they

have an equal number of electrons and neutrons

Atoms with the same number of protons but different numbers of neutrons

isotopes

All of the elements in group 2/2A will have the following charge:

+2

How many electrons does the following element have?

10