Q: A photon has a wavelength of $$4.00 \times 10$$^{-7}$$\ \mathrm{m}. $$What is its energy? (Use $$h = 6.626 \times 10$$^{-34}$$\ \mathrm{J\cdot s}$$ and $$c = 3.00 \times 10^8$\ \mathrm{m/s})$$

$$4.97 \times 10$$^{-19}$$\ \mathrm{J}$$

Q: Calculate the de Broglie wavelength of an electron ($$m = 9.11 \times 10$$^{-31}$$\ \mathrm{kg}) $$moving at $$2.00 \times 10^6$\ \mathrm{m/s}$$. ($$h = 6.626 \times 10$$^{-34}$$\ \mathrm{J\cdot s})$$

$$3.63 \times 10$$^{-10}$$\ \mathrm{m}$$

Question 1

Which of the following statements best explains why the noble gases are generally unreactive?

Accepted Answer

Noble gases have completely filled valence electron shells, making them energetically stable and unlikely to gain or lose electrons.

Question 2

A sample of magnesium contains 78.99% $$^{24}\mathrm{Mg} (23.985 $$amu), 10.00% $$^{25}\mathrm{Mg} (24.986 $$amu), and 11.01% $$^{26}\mathrm{Mg} (25.983 $$amu). What is the weighted average atomic mass of magnesium?

Accepted Answer

$$24.31\ \mathrm{amu}$$

Question 3

Which experiment provided the first evidence that atoms contain a small, dense, positively charged nucleus?

Accepted Answer

Rutherford's gold-foil experiment

Question 4

Which of the following sets of quantum numbers is NOT valid for an electron in an atom?

Accepted Answer

$$n=2,\ l=2,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 5

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

Accepted Answer

17 protons, 18 neutrons, 17 electrons

Question 6

Which of the following best describes the law of multiple proportions?

Accepted Answer

When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers.

Question 7

Which element is most likely to be a good conductor of electricity and form basic oxides?

Accepted Answer

Potassium ($$K$$), an alkali metal

Question 8

A photon has a wavelength of $$4.00 	imes 10$$^{-7}$$\ \mathrm{m}. $$What is its energy? (Use $$h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J\cdot s}$$ and $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$4.97 	imes 10$$^{-19}$$\ \mathrm{J}$$

Question 9

Which electronic transition in the hydrogen atom emits the highest-energy photon?

Accepted Answer

$$n=3 \rightarrow n=1$$

Question 10

Calculate the de Broglie wavelength of an electron ($$m = 9.11 	imes 10$$^{-31}$$\ \mathrm{kg}) $$moving at $$2.00 	imes 10^6$\ \mathrm{m/s}$$. ($$h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J\cdot s})$$

Accepted Answer

$$3.63 	imes 10$$^{-10}$$\ \mathrm{m}$$

Question 11

Which of the following electron configurations represents a valid ground state for a neutral atom?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^5$$

Question 12

Which of the following statements about periodic trends is correct?

Accepted Answer

Atomic radius decreases across a period from left to right due to increasing effective nuclear charge.

Question 13

A sample contains $$3.01 	imes 10$$^{23}$$ atoms of carbon. What is the mass of this sample? (Molar mass of carbon = 12.01$$\ \mathrm{g/mol}$$, Avogadro's number = 6.022$$ 	imes $$10^{23}$$\ \mathrm{mol}^{-1}$$)

Accepted Answer

$$6.00\ \mathrm{g}$$

Question 14

Which of the following pairs are isotopes of each other?

Accepted Answer

$$^{14}\mathrm{C}$$ and $$^{12}\mathrm{C}$$

Question 15

Which of the following best explains why the emission spectrum of hydrogen consists of discrete lines?

Accepted Answer

Electrons in hydrogen can only occupy specific, quantized energy levels, so only certain photon energies are emitted during transitions.

Question 16

Which of the following statements about the Pauli exclusion principle is correct?

Accepted Answer

No two electrons in the same atom can have the same set of four quantum numbers.

Question 17

A 10.0 g sample of calcium reacts completely with oxygen to form 14.0 g of calcium oxide. According to the law of conservation of mass, what mass of oxygen reacted?

Accepted Answer

$$4.0\ \mathrm{g}$$

Question 18

Which of the following best describes Hund's rule?

Accepted Answer

Electrons occupy degenerate orbitals singly before pairing up.

Question 19

Which of the following elements is a metalloid and is commonly used in computer chips due to its semiconducting properties?

Accepted Answer

Silicon ($$Si)$$

Structure, Stability, and Periodicity of Atoms: Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard