Module 3 Lessons 1-3

Which main part of Dalton's theory was discovered to be not true?

• Chemical reactions separate and rearrange atoms

• Atoms combine in whole number ratios to become compounds

• The atom is indivisible.

• Atoms of the same element are the same.

Answer explanation

The atom is made up of smaller parts.

Thomson's cathode ray experiment

• showed that there was a particle smaller than the atom

• the small particle was negatively charged

• led to the plum pudding model

• showed that the atom had a lot of empty space

Atomic theory changed from Thomson's model to Rutherford

• to show the empty space an atom has

• to show the electrons are in the nucleus

• to show the neutrons are in the nucleus

• to show a small dense nucleus

What are the important conclusion/s that came from Rutherford's Gold Foil Experiment?

• atoms of made up of protons and electrons

• atoms have a dense small nucleus

• atoms have equal number of protons and electrons

• atoms a lot of empty space around the nucleus

Answer explanation

Most alpha particles went through (did not hit anything, therefor empty space), some particles had small deflection ~ electron, and some bounced back ~ dense nucleus.

Protons and neutrons are found in the ___

The subatomic particles have the following charges

• protons are negative, neutrons are positive, and electrons and neutral

• protons are positive, neutrons are negative, and electrons and neutral

• protons are neutral, neutrons are positive, and electrons and negative

• protons are positive, neutrons are neutral, and electrons and negative

An ion has a charge of -3 and atomic number of 33. What element is it?

• Zinc

• Arsenic

• Krypton

• Nitrogen

Answer explanation

Atomic number determine the element. Atomic number is 33 ~ Arsenic

An ion has a charge of -3 and atomic number of 33. How many electrons are there

• 36

• 33

• 30

Answer explanation

protons - charge = number of electrons; 33 - (-3) = 36

What is the mass number of Iodine-131?

• 53

• 131

• 129

• 78

Answer explanation

When given an element name with a number, the number is the mass number.

How many protons does Iodine-131 have?

• 53

• 131

• 129

• 78

Answer explanation

Iodine's atomic number (look at the periodic table) is 53. Atomic number = number of protons. Number of protons = 53