Question 1

Which experiment provided evidence for the existence of a small, dense, positively charged nucleus at the center of the atom?

Accepted Answer

Rutherford's gold foil experiment

Question 2

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes have the same number of protons and electrons but different numbers of neutrons.

Question 3

Which type of radiation has the greatest penetrating power and requires lead shielding for protection?

Accepted Answer

Gamma rays

Question 4

What is the maximum number of electrons that can occupy the third energy level ($$n=3) $$according to the Bohr model?

Accepted Answer

$$18$$

Question 5

Which of the following electron configurations represents an atom in an excited state?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^3$$ $$3s^1$$

Question 6

A neutral atom of chlorine has an atomic number of 17 and a mass number of 35. How many neutrons does it have?

Accepted Answer

$$18$$

Question 7

Which group in the periodic table contains elements with the outer electron configuration $$ns^2np^5$?

Accepted Answer

Group 7A (Halogens)

Question 8

Which property is characteristic of metals but not of non-metals?

Accepted Answer

Good electrical conductivity

Question 9

The atomic mass of an element as shown on the periodic table is best described as:

Accepted Answer

The weighted average mass of all naturally occurring isotopes

Question 10

Which of the following best explains why different elements produce different colors in a flame test?

Accepted Answer

Electrons in each element occupy unique energy levels, emitting photons of specific energies when returning to lower states.

Question 11

Which of the following is a correct electron configuration for potassium ($$K$$, atomic number 19)?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^6$$ $$4s^1$$

Question 12

Which of the following statements about the modern periodic table is true?

Accepted Answer

Elements are arranged by increasing atomic number.

Question 13

A smoke detector uses a radioactive source that emits alpha particles. Why are alpha particles suitable for this application?

Accepted Answer

Alpha particles are easily stopped by air and do not pose a significant external hazard.

Question 14

Which of the following best describes the quantum mechanical model of the atom?

Accepted Answer

Electrons occupy orbitals, which are regions of space with a high probability of finding an electron.

Question 15

How many valence electrons does an atom of selenium (Se, atomic number 34) have?

Accepted Answer

$$6$$

Question 16

Which of the following is a property of transition metals?

Accepted Answer

They often form vibrantly colored complexes.

Question 17

Which of the following is the correct symbol for an isotope of oxygen with 8 protons and 10 neutrons?

Accepted Answer

$$^{18}_{8}O$$

Question 18

Which of the following best explains why Mendeleev's periodic table was considered revolutionary?

Accepted Answer

He left spaces for undiscovered elements and predicted their properties.

Question 19

Which of the following is a real-world consequence of exposure to ionizing radiation?

Accepted Answer

Formation of ions that can damage DNA and potentially cause cancer

Question 20

How many electrons can be held in all the orbitals of the $$n=2$$ principal energy level?

Accepted Answer

$$8$$

Atomic Structure and the Periodic Table: Study Notes

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