Question 1

Which property of hydrogen gas made it suitable for use in the Hindenburg airship, and what was the associated risk?

Accepted Answer

Hydrogen is less dense than air, providing buoyancy, but it is highly reactive and flammable.

Question 2

Why is helium used in modern blimps instead of hydrogen?

Accepted Answer

Helium is inert due to its stable electron configuration, making it nonflammable and safe.

Question 3

According to Mendeleev's periodic law, what is observed when elements are arranged by increasing atomic number?

Accepted Answer

Certain sets of properties recur periodically.

Question 4

Which model of the atom first explained the emission spectrum of hydrogen?

Accepted Answer

Bohr model

Question 5

What is the relationship between wavelength ($$\lambda) $$and frequency ($$
u) of $$electromagnetic radiation?

Accepted Answer

They are inversely proportional: $$\lambda \propto \frac{1}{
u}$$

Question 6

Arrange the following types of electromagnetic radiation in order of increasing energy per photon: microwaves, visible light, X-rays.

Accepted Answer

Microwaves \u003c Visible light \u003c X-rays

Question 7

Which type of electromagnetic radiation is most likely to cause damage to biological molecules due to its high energy?

Accepted Answer

Gamma rays

Question 8

What is a photon?

Accepted Answer

A particle of light, representing a single packet of energy

Question 9

In the Bohr model, what happens when an electron in a hydrogen atom relaxes from a higher-energy orbit to a lower-energy orbit?

Accepted Answer

A photon is emitted with energy corresponding to the difference between the two orbits.

Question 10

Which statement best describes the quantum-mechanical model of the atom?

Accepted Answer

Electrons exist in probability maps called orbitals, which show where they are likely to be found.

Question 11

What is the principal quantum number ($$n) $$and what does it specify?

Accepted Answer

It specifies the principal shell and energy level of an orbital.

Question 12

Which rule states that orbitals of identical energy are first occupied singly by electrons with parallel spins before pairing occurs?

Accepted Answer

Hund's rule

Question 13

How many valence electrons does chlorine have, and why?

Accepted Answer

7, because it is in group 7A of the periodic table

Question 14

Which element has the electron configuration $$[Ne]3s^1$?

Accepted Answer

Sodium

Question 15

What is the trend in atomic size as you move down a group in the periodic table?

Accepted Answer

Atomic size increases because the principal quantum number ($$n) $$increases.

Question 16

Which of the following best explains why noble gases are inert?

Accepted Answer

They have a completely filled s and p orbital in their outermost shell, resulting in 8 valence electrons.

Question 17

Which periodic trend describes the change in ionization energy as you move to the right across a period?

Accepted Answer

Ionization energy increases.

Question 18

What is the effect of ionizing radiation, such as X-rays and gamma rays, on biological molecules?

Accepted Answer

It can permanently change or destroy biological molecules by ionizing them.

Question 19

Which orbital is higher in energy in a multi-electron atom: 4s or 3d?

Accepted Answer

4s is lower in energy than 3d.

Question 20

Which statement about valence electrons is correct?

Accepted Answer

Valence electrons are found in the outermost principal shell and are involved in chemical bonding.

Electrons in Atoms and the Periodic Table: Study Notes

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