Intro To Chapter 2 Quiz

Explanation
The question is asking for the number of protons. The correct answer is 5 because the atomic number of an element represents the number of protons in its nucleus. Since the question does not specify the element, we can assume it is referring to the atomic number of boron, which is 5.

Explanation
The atomic number of an element represents the number of protons in its nucleus. In this case, the element is 18O, which means it has 18 nucleons (protons + neutrons) in total. Since the atomic number is given as 8, it indicates that there are 8 protons in the nucleus of 18O.

Explanation
The question is asking for the number of electrons in an atom with the symbol 18O-2. The symbol 18O represents an oxygen atom with a mass number of 18, which means it has 18 protons and 18 neutrons. The -2 charge indicates that the atom has gained 2 extra electrons. Since the number of electrons in a neutral atom is equal to the number of protons, and the atom now has 2 extra electrons, the total number of electrons is 18 + 2 = 20. Therefore, the correct answer is 10, as it is the closest option to 20.

Explanation
The atomic number of oxygen is 8, which indicates the number of protons in the nucleus. The mass number of oxygen is 18, which represents the total number of protons and neutrons in the nucleus. To find the number of neutrons, subtract the atomic number from the mass number. Therefore, 18 - 8 = 10 neutrons.

Explanation
The element with 11 protons is sodium. The atomic number of an element is equal to the number of protons it has, so since sodium has 11 protons, it matches the given information. The number of neutrons and electrons is not relevant to determining the element in this case.

Explanation
The atomic mass of an element is determined by the sum of the number of protons and neutrons in its nucleus. In this case, the element has 11 protons and 12 neutrons, so the atomic mass is 11 + 12 = 23.

Explanation
The atomic number of an element is equal to the number of protons in its nucleus. In this case, the element has 11 protons, so its atomic number is 11.

Explanation
The element has 11 protons and 10 electrons, which means it has a net positive charge of +1. This is because protons have a positive charge and electrons have a negative charge. The number of protons determines the element's atomic number, while the number of electrons determines its overall charge. In this case, the element has one more proton than electrons, resulting in a net positive charge of +1.

Explanation
18O and 16O are isotopes because they have the same number of protons but different numbers of neutrons. Isotopes are variants of an element that have the same atomic number but different atomic masses. In this case, both atoms are oxygen atoms (with 8 protons), but 18O has 10 neutrons while 16O has 8 neutrons.

Explanation
The atomic number of an atom represents the number of electrons it has. In this case, the atom is calcium (Ca) with an atomic number of 20, which means it normally has 20 electrons. However, the question specifies that the calcium ion has a +2 charge (Ca+2). This indicates that the atom has lost 2 electrons, resulting in a total of 18 electrons. Therefore, the correct answer is 18.

Explanation
The atomic number of an atom represents the number of protons in its nucleus. In this case, the atom is 42Ca+2, which means it has a charge of +2. The atomic number of calcium (Ca) is 20, indicating that it has 20 protons. Since the charge is +2, there are two more protons than electrons, resulting in a net positive charge. Neutrons, on the other hand, have no charge. To find the number of neutrons, subtract the atomic number from the mass number. The mass number of calcium is approximately 42, so subtracting 20 (the atomic number) from 42 gives us 22 neutrons.

Explanation
If you were to add one proton to the atom 42Ca+2, the atomic symbol would change from Ca to a different element, as the number of protons determines the identity of the element. Additionally, the atomic number would increase from 42 to 43, indicating the number of protons in the nucleus. The charge of the atom would also change from +2 to +1, as the number of protons would exceed the number of electrons by one.