Question

elements and the periodic table — how much do you remember?
goal :assess your recall and understanding of ideas about the atom and the periodic table from earlier
grades
true or false? each of the statements below is either true or false. if the statement is true, write the
letter t beside its number. if false, write the letter f and rewrite the statement so that it is true.
10ns

1. a particle that gains electrons is called a cation.
2. the symbol 27/13al represents an atom that has 27protons and 13 neutrons.
3. elements that have the same number of energy levels have similar chemical

properties.

1. the lewis structure for an atom of neon, ne, has 8 dots around the element

symbol.

1. the atom has a sharply defined outer boundary.
2. elements in the periodic table are arranged in order of increasing atomic

mass.

1. of the elements, helium, iron, sulfur, calcium, and potassium, the one that

would react in a way that is most like sodium is calcium.

1. neutrons and electrons have nearly identical masses.
2. neutral atoms have the same number of protons and electrons.
3. there is no limit to the number of electrons that can occupy the energy levels

surrounding an atom.

1. given the choice of aluminum, magnesium, oxygen, helium, and hydrogen,

the element that is most stable is oxygen.

1. hydrogen-1, hydrogen-2, and hydrogen-3, are elements that have the same

number of protons but different numbers of electrons.

1. the lewis structure for an element that has an atomic number of 12 would

have 2 dots, with both dots placed together on the same side of the element
symbol.

1. a fluorine ion has 7 valence electrons.

Explanation:

Step1: Analyze statement 1

A particle that gains electrons is negatively charged and is called an anion. A cation is a positively - charged particle (loses electrons). So, statement 1 is false.

Step2: Analyze statement 2

In the notation \(_{13}^{27}\text{Al}\), the lower number (13) is the atomic number (number of protons) and the upper number (27) is the mass number (protons + neutrons). So, neutrons \(=27 - 13=14\). Statement 2 is false.

Step3: Analyze statement 3

Elements in the same group (vertical column) have similar chemical properties as they have the same number of valence electrons. Elements in the same period (horizontal row) have the same number of energy levels but different chemical properties. Statement 3 is false.

Step4: Analyze statement 4

Neon (\(\text{Ne}\)) has 8 valence electrons. In a Lewis structure, we represent valence electrons as dots. So, there are 8 dots around the \(\text{Ne}\) symbol. Statement 4 is true.

Step5: Analyze statement 5

An atom does not have a sharply defined outer boundary. The electron cloud model describes the probability of finding an electron in a region around the nucleus. Statement 5 is false.

Step6: Analyze statement 6

Elements in the periodic table are arranged in order of increasing atomic number (number of protons), not atomic mass. Statement 6 is false.

Step7: Analyze statement 7

Sodium (\(\text{Na}\)) is in group 1. Potassium (\(\text{K}\)) is also in group 1. Calcium (\(\text{Ca}\)) is in group 2. Elements in the same group have similar chemical properties. So, potassium would react more like sodium than calcium. Statement 7 is false.

Step8: Analyze statement 8

Neutrons have a mass of approximately \(1.6749\times10^{-27}\text{ kg}\) and electrons have a mass of approximately \(9.1094\times 10^{-31}\text{ kg}\). Their masses are not nearly identical. Statement 8 is false.

Step9: Analyze statement 9

In a neutral atom, the number of protons (positive charge) is equal to the number of electrons (negative charge) to balance the charge. Statement 9 is true.

Step10: Analyze statement 10

Each energy level has a limit to the number of electrons it can hold. For example, the first energy level (\(n = 1\)) can hold a maximum of 2 electrons, the second (\(n=2\)) can hold a maximum of 8 electrons. Statement 10 is false.

Step11: Analyze statement 11

Helium (\(\text{He}\)) is a noble gas with a full valence shell (2 electrons in the first energy level). Noble gases are the most stable. Oxygen (\(\text{O}\)) has 6 valence electrons and is more reactive. Statement 11 is false.

Step12: Analyze statement 12

Hydrogen - 1, hydrogen - 2, and hydrogen - 3 are isotopes. Isotopes have the same number of protons but different numbers of neutrons. In a neutral state, they have the same number of electrons (equal to the number of protons). Statement 12 is false.

Step13: Analyze statement 13

An element with atomic number 12 is magnesium (\(\text{Mg}\)). Magnesium has 2 valence electrons. In a Lewis structure, the two dots are placed separately (not together) around the \(\text{Mg}\) symbol. Statement 13 is false.

Step14: Analyze statement 14

A fluorine atom (\(\text{F}\)) has 7 valence electrons. When it forms an ion (\(\text{F}^-\)), it gains 1 electron, so it has 8 valence electrons. Statement 14 is false.

Answer:

1. F, A particle that gains electrons is called an anion.
2. F, The symbol \(_{13}^{27}\text{Al}\) represents an atom that has 13 protons and 14 neutrons.
3. F, Elements that have the same number of valence electrons have similar chemical properties.
4. T
5. F, The atom does not have a sharply defined outer boundary.
6. F, Elements in the periodic table are arranged in order of increasing atomic number.
7. F, Of the elements, helium, iron, sulfur, calcium, and potassium, the one that would react in a way that is most like sodium is potassium.
8. F, Neutrons and protons have nearly identical masses.
9. T
10. F, There is a limit to the number of electrons that can occupy the energy levels surrounding an atom.
11. F, Given the choice of aluminum, magnesium, oxygen, helium, and hydrogen, the element that is most stable is helium.
12. F, Hydrogen - 1, hydrogen - 2, and hydrogen - 3, are elements that have the same number of protons but different numbers of neutrons.
13. F, The Lewis structure for an element that has an atomic number of 12 (magnesium) would have 2 dots, with the dots placed separately around the element symbol.
14. F, A fluorine ion has 8 valence electrons.