$$(0.60 \times 10) + (0.40 \times 12) = 6 + 4.8 = 10.8$$ amu

Question 1

Which statement best describes the main conclusion from Rutherford's gold foil experiment?

Accepted Answer

Most of the atom's mass and all of its positive charge are contained in a small, dense nucleus.

Question 2

A neutral atom of magnesium has an atomic number of 12 and a mass number of 24. How many neutrons does it contain?

Accepted Answer

$$24 - 12 = 12$$ neutrons

Question 3

Which property is NOT characteristic of metals?

Accepted Answer

They tend to gain electrons during chemical reactions.

Question 4

Which of the following best explains why chlorine-37 is an isotope of chlorine-35?

Accepted Answer

They have the same number of protons but different numbers of neutrons.

Question 5

A fluorine atom gains one electron to form an ion. What is the charge of the resulting ion?

Accepted Answer

$$9 - 10 = -1 (1- $$charge)

Question 6

Which of the following elements is a noble gas and why is it chemically unreactive?

Accepted Answer

Neon; it has a complete outer energy level of electrons.

Question 7

Which scientist is credited with the discovery of the electron, and what experiment led to this discovery?

Accepted Answer

J.J. Thomson; cathode ray tube experiment

Question 8

Calculate the atomic mass of an element with two isotopes: 60% with mass 10 amu and 40% with mass 12 amu.

Accepted Answer

$$(0.60 	imes 10) + (0.40 	imes 12) = 6 + 4.8 = 10.8$$ amu

Question 9

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 10

Which group of elements is most likely to form ions with a $$2+$$ charge, and why?

Accepted Answer

Alkaline earth metals; they have two valence electrons that they lose easily.

Question 11

A radioactive isotope is used in medical imaging. Which property makes it useful for this application?

Accepted Answer

It emits detectable nuclear radiation that can be traced inside the body.

Question 12

Which of the following best describes the difference between a cation and an anion?

Accepted Answer

A cation has more protons than electrons, while an anion has more electrons than protons.

Question 13

Which of the following is a correct example of isotope notation for an atom with 6 protons and 8 neutrons?

Accepted Answer

$$^{14}_{6}\mathrm{C}$$

Question 14

Which of the following best explains why elements in the same group (column) of the periodic table have similar chemical properties?

Accepted Answer

They have the same number of valence electrons.

Question 15

Which of the following is NOT a property of nonmetals?

Accepted Answer

They are good conductors of heat and electricity.

Question 16

A sample of chlorine contains 75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu). What is the atomic mass of chlorine?

Accepted Answer

$$(0.7577 	imes 34.97) + (0.2423 	imes 36.97) = 26.50 + 8.96 = 35.46$$ amu

Question 17

Which of the following statements about the periodic law is correct?

Accepted Answer

When elements are arranged in order of increasing atomic number, certain sets of properties recur periodically.

Question 18

Which of the following best describes the charge and mass of a neutron?

Accepted Answer

No charge; mass nearly equal to a proton

Atoms and Elements: Foundations of Matter and the Periodic Table

Guida di studio - Domande di pratica