Chemistry 101 Week 3

Periodic Period

A horizontal row of elements in the periodic table

How many electrons does Na+ contain? Provide your answer below:

Correct answers: 10 electrons The following equation can be used to determine the number of electrons in an element. overall charge=number of protons−number of electrons The overall charge of the ion is +1. Rearranging and using the atomic number for the number of protons, we can solve for the number of electrons: number of electrons=number of protons−overall charge number of electrons=11−(+1)=10

What is the atomic mass of xenon? Your answer should have six significant figures.

Correct answers: 131.294 amu Xenon has an atomic mass of 131.294 amu and an atomic number of 54.

Periodic Groups

Vertical columns on the periodic table 1-18

Element

A pure substance that cannot be broken down into simpler substances

atomic symbol

An abbreviation for an element or atom

How many electrons are in the n=3 shell for sodium? Select the correct answer below: 1 2 3 4

Correct answer: 1 Sodium has an atomic number of 11, meaning it has 11 protons and therefore 11 electrons. An electron arrangement, written (i,j,k,...), describes how many electrons are in each occupied energy level, starting with n=1. Since sodium is one of the first 20 elements, the electron arrangement can be found by filling energy levels in increasing order of the energy level, n, until all the electrons have been accounted for. The first shell, n=1, can hold up to 2 electrons, so 2 of the 11 electrons in oxygen will occupy the first shell. This leaves 11−2=9 electrons to place. The second shell can hold up to 8 electrons, so the 8 of the remaining electrons will be in the n=2 level and the 1 remaining electron will be in the third level.

Determine the number of neutrons in the isotope 176Hf. Provide your answer below:

Correct answers: 104 neutrons The following equation can be used to determine the number of neutrons in an element. mass number=number of protons+number of neutrons Rearranging and using the atomic number for the number of protons, we can solve for the number of neutrons: number of neutrons=mass number−number of protons number of neutrons=176−72=104

Find the number of protons, neutrons, and electrons in 6429Cu. Provide your answer below: protons, neutrons, eletrons

Correct answers: 29 protons, 35 neutrons, 29 electrons Start by using the atomic number from the symbol 64 29 Cu to find the number of protons. The 29 in the lower left is the atomic number, which means it is also the number of protons. In an uncharged atom, the number of protons matches the number of electrons, so there are also 29 electrons. The mass number is written in the upper left corner and is equal to the number of protons and neutrons. Writing the equation and solving for the number of neutrons gives mass number/number of neutrons=number of protons+number of neutrons=mass number−number of protons=64−29=35 Therefore, 6429Cu has 29 protons, 35 neutrons, and 29 electrons.

Determine the number of neutrons in the isotope bromine-81. Provide your answer below:

Correct answers: 46 neutrons The following equation can be used to determine the number of neutrons in an element. mass number=number of protons+number of neutrons Rearranging and using the atomic number for the number of protons, we can solve for the number of neutrons: number of neutrons=mass number−number of protons number of neutrons=81−35=46

How many electrons are in the n=4 shell of potassium? Select the correct answer below: 1 2 4 8

Correct answer: 1 The element that has two more protons than chlorine is potassium. Potassium has an atomic number of 19, meaning it has 19 protons and, therefore, 19 electrons. An electron arrangement, written (i,j,k,...), describes how many electrons are in each occupied energy level, starting with n=1. Since potassium is one of the first 20 elements, the electron arrangement can be found by filling energy levels in increasing order of the energy level, n, until all the electrons have been accounted for. The first shell, n=1, can hold up to 2 electrons, so 2 of the 19 electrons in potassium will occupy the first shell. This leaves 19−2=17 electrons to place. The second shell can hold up to 8 electrons, so 8 of the remaining electrons will be in the n=2 level, leaving 9. 8 of those remaining electrons will be in the third level because the fourth shell starts to fill when there are 8 electrons in the third shell; the final electron will be in fourth level.

How many electrons are in the n=4 shell of the twentieth element in the periodic table? Select the correct answer below: 1 2 7 8

Correct answer: 2 The twentieth element is calcium, with an atomic number of 20, 20 protons, and 20 electrons. An electron arrangement, written (i,j,k,...), describes how many electrons are in each occupied energy level, starting with n=1. Since calcium is one of the first 20 elements, the electron arrangement can be found by filling energy levels in increasing order of the energy level, n, until all the electrons have been accounted for. The first shell, n=1, can hold up to 2 electrons, so 2 of the 20 electrons in calcium will occupy the first shell. This leaves 20−2=18 electrons to place. The second shell can hold up to 8 electrons, so 8 of the remaining electrons will be in the n=2 level, leaving 10. 8 of those remaining electrons will be in the third level because the fourth shell starts to fill when there are 8 electrons in the third shell; the final two electrons will be in fourth level.

Which of the following is true according to Dalton's atomic theory? Select the correct answer below: Atoms cannot be created or destroyed. Atoms of the same element will have differing sizes and masses. Elements can consist of many types of atoms. All of the above are true.

Correct answer: Atoms cannot be created or destroyed. Dalton's atomic theory states that atoms can not be created or destroyed. This is consistent with the law of conservation of matter. If a chemical change is simply the rearrangement of atoms, and atoms are not created or destroyed when participating in a chemical change, this explains how matter is conserved in any chemical reaction.

Which element has an electron configuration ending in 4p5? Select the correct answer below: Br Se I Kr

Correct answer: Br Bromine is in period 4 and is the fifth element in the corresponding p block, so its electron configuration will end in 4p5.

Which element has the electron configuration 1s22s22p63s23p64s23d104p65s24d105p66s24f7? Select the correct answer below: Eu Sm Os Am

Correct answer: Eu The f block is two behind the period number in terms of energy level, and europium is the 7th element in the f block for period 6. This means europium will have an electron configuration ending in 6s24p7.

Which element has an atomic mass of approximately 59 amu? Select the correct answer below: Pr Ni Cu Am

Correct answer: Ni Nickel has an atomic mass of 58.693 amu. This is the closest atomic mass to 59 amu of the answer choices.

Which of the following is a correct statement about different elements that are in the same group in the periodic table? Select the correct answer below: They have the same atomic number. They have different chemical properties. They are in the same column of the periodic table. They are in the same row of the periodic table.

Correct answer: They are in the same column of the periodic table. The vertical columns in the periodic table are called groups. Elements in the same column or group of the periodic table often have similar chemical properties.

Which has the smallest mass? Select the correct answer below: an atom a proton a neutron an electron

Correct answer: an electron Electrons have much less mass than protons and neutrons, and all of these are much smaller than an atom.

Which element belongs to the alkaline earth metals? Select the correct answer below: aluminum sodium calcium chromium

Correct answer: calcium Calcium belongs to the alkaline earth metals.

Atoms of the same element can have different: Select the correct answer below: atomic numbers mass numbers numbers of protons none of the above

Correct answer: mass numbers Atoms of the same element must have the same number of protons, as this defines their atomic number which is characteristic of that element. But they may have differing numbers of neutrons which would generate a different mass number.

Which element belongs to the transition metals? Select the correct answer below: sodium boron aluminum nickel

Correct answer: nickel Nickel belongs to the transition metals.

All of the following are transition metal elements except: Select the correct answer below: silicon mercury iron titanium

Correct answer: silicon Mercury (Hg), iron (Fe), and titanium (Ti) are transition metal elements. Silicon (Si) is a metalloid, an element that conducts heat and electricity moderately well and possesses properties of both metals and nonmetals.

The prefix in subatomic tells us that subatomic particles are: Select the correct answer below: particles made of atoms the basic building blocks of atoms particles of similar size to atoms particles that power nuclear submarines

Correct answer: the basic building blocks of atoms The prefix "sub" can mean below, under, or imply that something is more basic than something else. All of these contexts can apply here, to state that subatomic particles are less massive than atoms, take up less space than atoms, or more generally that they comprise atoms.

Which of the following is used to abbreviate an element or an atom of a given element? Select the correct answer below: the mass number the atomic mass the chemical symbol the atomic number

Correct answer: the chemical symbol An element is is a substance that cannot be broken down or changed. Each element is represented with a chemical symbol which is an abbreviation for the element or an atom of an element.