Question 1

Which of the following best explains why helium is used in modern blimps instead of hydrogen?

Accepted Answer

Helium is an inert gas with a stable electron configuration, making it non-reactive and safe.

Question 2

Which statement correctly describes the relationship between wavelength ($$\lambda) $$and frequency ($$
u) of $$electromagnetic radiation?

Accepted Answer

Wavelength and frequency are inversely proportional, as described by $$c = \lambda 
u.$$

Question 3

A photon of ultraviolet light has a shorter wavelength than a photon of visible light. What does this imply about its energy?

Accepted Answer

It has more energy than visible light, as energy is inversely related to wavelength: $$E = \dfrac{hc}{\lambda}.$$

Question 4

Which of the following types of electromagnetic radiation has the highest energy per photon?

Accepted Answer

Gamma rays

Question 5

The emission spectrum of hydrogen contains distinct lines at specific wavelengths. What does this observation support?

Accepted Answer

Electrons in hydrogen atoms occupy quantized energy levels, as described by the Bohr model.

Question 6

According to the quantum-mechanical model, what does an orbital represent?

Accepted Answer

A probability map showing where an electron is likely to be found.

Question 7

Which principle states that no more than two electrons can occupy the same orbital, and they must have opposite spins?

Accepted Answer

Pauli exclusion principle

Question 8

What is the electron configuration for a ground-state carbon atom?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^2$$

Question 9

Which element is most likely to form a $$1^+$$ ion in chemical reactions?

Accepted Answer

Sodium

Question 10

As you move down a column in the periodic table, what happens to atomic size and ionization energy?

Accepted Answer

Atomic size increases and ionization energy decreases.

Question 11

Which of the following best describes the electron configuration of chlorine using noble gas core notation?

Accepted Answer

$$[Ne] 3s^2$ 3p^5$

Question 12

Which periodic trend is responsible for the increased reactivity of alkali metals as you move down the group?

Accepted Answer

Increasing atomic size and decreasing ionization energy

Question 13

Which block of the periodic table contains the transition metals?

Accepted Answer

d block

Question 14

A red shirt appears red because:

Accepted Answer

It reflects red light and absorbs other colors.

Question 15

Which of the following is the correct order of increasing energy per photon for visible light, X-rays, and microwaves?

Accepted Answer

Microwaves \u003c Visible light \u003c X-rays

Question 16

Which quantum number specifies the principal shell of an orbital?

Accepted Answer

Principal quantum number ($$n)$$

Question 17

Which rule states that electrons occupy orbitals of equal energy singly before pairing?

Accepted Answer

Hund's rule

Question 18

Which of the following elements has 6 valence electrons?

Accepted Answer

Oxygen

Question 19

What is the main reason noble gases are chemically inert?

Accepted Answer

They have completely filled valence shells, making them stable.

Question 20

Which of the following statements about metallic character is correct?

Accepted Answer

Metallic character increases as you move down a column and decreases as you move to the right across a period.

Electrons in Atoms and the Periodic Table: Models, Configurations, and Periodic Trends

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