Question

The mystery of periodic law was solved when __________ proposed his planetary atomic model of the atom, providing an understanding of the electronic structure of the elements and the organization of electrons into shells.
A) Bohr
B) Rutherford
C) Heisenberg
D) Schrödinger

Chris the Chemist was working in the lab, and he wanted to see what would happen if he put copper chloride into a Bunsen burner flame. As soon as he put it in the flame, it began to emit a green color. Which of these BEST describes this outcome?
A) The heat split the nucleus and created a new element.
B) As the copper chloride was heated, electrons were turned into neutrons.
C) As the electrons moved to a higher energy level, a photon of light is emitted.
D) When excited electrons return back to the ground state, a photon of light is emitted.

Boron has two naturally-ocurring isotopes. Boron-10 has an abundance of 19.8% and actual mass of 10.013 amu, and boron-11 has an abundance of 80.2% and actual mass of 11.009 amu. What is the average atomic mass for all isotopes of boron?
A) 10.0 amu
B) 10.5 amu
C) 10.511 amu
D) 10.812 amu

Answer 1

Answer:

1.A

2.D

3.D

Explanation:

1.We have to fill correct answer  in blank  space given in the question.

Bohr's postulates

1.Electron revolve in certain stable  orbits around the nucleus without radiating any energy .The stable orbits or energy levels  are called stationary orbits and these orbits at a certain discrete distance from the nucleus.

2.The stationary orbits are attained at distances for which the  angular momentum is integral multiple of plank;s constant

L=mvr=nh

Where n is called principle quantum number

3.Electrons gain or lose energy when they jump from one energy lever to other energy lever or when higher energy level to low energy level.

Hence, the mystery of periodic laws was solved when Bohr proposed his planetary atomic model of the atom ,providing an understanding of the electronic structure of the elements and the organization of electrons into shells,

Option A is true.

2.When am electron absorb energy then the electrons jump from low energy level to high energy level .When the electron return from higher energy level to low energy level then it emit colored flame.

When Christ put copper chloride into Bunsen burner flame then it began to emit a green color because when excited electron returns back to the ground state , then  photon of light is emitted.

Hence, option D is true.

3.Boron-10 has abundance 19.8% and actual mass of 10.013 amu and boron-11 has an abundance of 80.2% and actual mass of 11.009.

We have to find the average atomic mass for all isotopes of boron

Average atomic mass of boron =$0.198\times 10.013+0.802\times 11.009$

Average atomic mass of boron=10.811792=10.812 amu

Hence, option D is true.

Answer 2

1. A) Bohr

2. D) When excited electrons return back to the ground state, a photon of light is emitted.

3. D) 10.812 amu

Hope this helps! :)