Question

Chemistry 1010 Test for Chapters 1-2-3-4 Name Several scientists made contributions to our present day understanding of the atom. Below are the names of 5 of these scientists. PICK OUT ANY 3 OF THES AND STATE WHAT THEIR CONTRIBUTION WAS. Democritus- Roentgen - Bohr- Heisenburg- JJ Thomson The following questions are multiple choice. Write or type in an X beside the answer you think is correct. 1. What is the term for the number of protons in the nucleus of an atom? a Atomic notation b. Atomic number c. Mass number d. Periodic Table number 2. What is the term for two atoms of the same element that have different numbers of neutrons in the nucleus? a Atomic twins b. Nucleons c Photons d. Isotopes 3. What is the term for the unit that is 1/12 the mass of a carbon-12 atom? a. Atomic mass unit b. Hydrogen mass unit c. Isotope mass unit d. Carbon mass unit 4. Which of the following can be separated into two or more pure substances by physical means? a Compound b. Element c. Mixture d Transitional 5. Which of the following properties of gasoline is a chemical property? a Boils at 97°C b. Density = 0.69 g/mL c. Combines with oxygen to form carbon dioxide and water d. Is a clear liquid

Answer 1

Neils bohr

- contribution to quantum physics- invented bohr model of atom that was also called liquid drop model and also the principle of correspondence and complementarity.

1913, Niels Bohr proposed a theory for the H atom based on quantum theory that energy is transferred only in certain well specified quantities. Electrons should be moving around the nucleus but only in the prescribed orbits not anywhere else.

Heisenberg

-In 1925, he invented Heisenberg uncertainity principle, "it is impossible to determine both the position and momentum of a smallest moving particle like electron".

JJ Thomson

-In 1897, discovered electron, using cathode ray tube. Stated that the cathode rays are negatively charged.

1. The correct answer is b) atomic number

Atomic number is defined as the number of protons in the nucleus.

Other options are not correct. a)atomic notation needs both atomic number and mass number

                                            c) Mass number is the sum of number of Protons and neutrons

                                            d) Periodic table number is otherwise regarded as atomic number

2. The correct answer is d) isotopes

Isotopes are defined as the two or more elements having same number of protons but different number of neutrons

Other options are not correct

a) Atomic twins is about crystal. These are compound crystal composed of 2 adjoining crystals of the same kind that commonly share a plane of atoms.

b) Nucleons also involve number of protons, despite number of neutrons.

c) Photons are bundles of energy that do not include neutrons.

3. The correct answers are a) atomic mass unit

Because the statement given in the question is the direct definition of a.m.u

Other options are not correct

b) Hydrogen mass unit explains about only for H isotopes

c) Isotope mass unit is not the correct term

d) Carbon mass unit, though it matches with the statement in the question, there is nothing like c.m.u in the place of a.m.u

4. The correct answer is c) Mixture

Because a 'mixture' has more than one component that vary by difference in properties and physically or chemically distinguishable. You can separate this by suitable physical methods.

Other options are not correct

a)compound- A compound will have only one component that is indistiguishable.

b) element- represent only one species that is indistinguishable

d) transitional-include intermdiate of species, but are indistinguishable

5. The correct answer is c)combines with Oxygen to form CO2 and water

Because it involves combustion reaction which is basically a chemically reaction

Other options are not correct

a)Boiling point is a physical property

b)Density is also a physical property

c) transparency or turbid appearance is also a physical property