Question

State true or false. 1. All atoms of an element contain the same number of neutrons. 2. Canal rays were discovered by E. Rutherford 3. Electrons contribute to the atomic mass of an atom. 4. Electrons move in orbits around the nucleus in an atom. 5. An element having atomic number 11 will exhibit valency of -1. 6. Iron exhibits variable valencies. ​

Answer 1

Explanation:

1. False - atoms of an element contain the same number of protons.
2. False - it is disocovered by Eugen Goldstein.
3. False - protons and neutrons contribute to atomic mass.
4. True
5. True
6. True

Answer 2

Answer:

• All atoms of an element contain the same number of neutrons- False
• Canal rays were discovered by E. Rutherford - False
• Electrons contribute to the atomic mass of an atom.  - False
• Electrons move in orbits around the nucleus in an atom - True  
• An element having atomic number 11 will exhibit valency of -1 - True
• Iron exhibits variable valences. ​ - True

Explanation:

• The number of protons in all atoms of an element is the same, but the number of neutrons can vary.  
• Canal Ray experiment is the experiment performed by German scientist Eugen Goldsteinin 1886 that led to the discovery of the proton.  
• Electrons are much smaller in mass than protons, weighing only $9.11 x 10^ {-28 }$grams, or about 1/1800 of an atomic mass unit. Therefore, they do not contribute much to an element's overall atomic mass.
• The electron travels in circular orbits around the nucleus.
• The electronic configuration is $1s^2 2s^2 2p^6 3s^1$so valency 1.
• In the formation of ferrous oxide, iron exhibits a valency of +2, whereas, in ferric oxide, it has a valency of +3. This is termed variable valency. Hence, Iron valency shows variable valency.