U2 Practice Phy Science

In a neutral atom, the number of protons is equal to the number of electrons.

True

Isotopes are forms of an element that have the same number of protons but a different number of electrons.

False

The modern periodic table is arranged from right to left in order of increasing atomic mass.

False

A proton is a subatomic particle carrying a charge equal to but opposite that of an electron.

True

1s22s22p63s23p64s23d104p65s2 is the correct electron configuration for the element Bromine.

False

*Valence* refers to the total number of electrons that exist in the orbitals that occupy the outermost energy level of an atom.

True

Elements in the same group (family) tend to have the same number of valence electrons.

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True

After conducting the Gold Foil experiment, which scientist described a positively charged core (“nucleus”) in the middle of a lot of empty space?

Rutherford

Which one is comprised of the other three?

atom

Which has a charge of +1?

proton

Which one(s) have a mass of 1 amu?

protons and neutron

Which is the smallest part of an element that retains all the properties of the element?

atom

Which is the correct symbol for the atom with 42 protons and 49 neutrons?

91

Mo

42

Which is the number of protons in Iron (Fe)?

26

Which is the number of neutrons in Cl-37?

20

Which element has 14 protons?

Silicon

Which is the correct number of valence electrons in the element Gallium (Ga)?

3

Which is the correct number of valence electrons in the element Sulfur (S)?

6

Which element has the electron configuration 1s22s22p63s23p64s23d4?

Chromium (Cr)

Which is the correct electron configuration for the element Molybdenum (Mo)?

1s22s22p63s23p64s23d104p65s24d4

Which of these elements has 5 valence electrons?

\
Arsenic (As)

How many valence electrons are present in silicon?

4

Which region is referred to as the f-block on the diagram?

B

Which region contains elements with two valence electrons?

A

Identify the period and group numbers of the element with the electron configuration. 1s22s22p63s23p4

Period 3, Group 16

How many electrons are found in a neutral atom of silicon (Si)?

14

Researchers discovered a subatomic particle while working with the cathode ray tube. The particle is known as a(n)

electron

A _ is a subatomic particle that has mass nearly equal to that of a proton, but it carries no electrical charge.

neutron

The number of protons in an atom is called the _ of the element.

atomic number

The number of _ determines the identity of the atom.

protons

Write the electron configuration of cesium if the atomic number is 55.

__1s22s22p63s23p64s23d104p65s24d105p66s1__

How many energy levels are present in yttrium (Y)? Answer with a number only.

5

Write the electron configuration for arsenic (As).

__1s22s22p63s23p64s23d104p3__

How many energy levels does krypton have? (Answer with a number only)

4

An element X has two naturally occurring isotopes: X-79 (abundance = 50.69%, mass = 78.918 amu) and X-81 (abundance = 49.31%, mass = 80.917 amu). Calculate the weighted atomic mass of X and identify the element. **Answer with the correct number of significant digits and units!**

Average atomic mass (No spaces, with units): _ \n Element name (No abbreviation): _

79\.90 amu; Bromine

Calculate the number of protons, electrons, and neutrons in an atom of the element Pb with mass number 207 and atomic number 82. \n \n Number of protons = _ \n Number of electrons = _ \n Number of neutrons = _

p=82;e=82;n=125

Uranium is used in nuclear reactors and is a rare element on earth. Uranium has three common isotopes. If the abundance of 234 U is 0.01%, the abundance of 235U is 0.71%, and the abundance of 238 U is 99.28%, what is the average atomic mass of uranium? **Round your answer to two decimal places!**

\n Average Atomic Mass (no spaces, with units)= _

237\.98