Question

chemistry fall semester final exam review (25-26)
the atom

1. which of the following determines what element the atom is?

a. the # of protons b. the # of electrons c. the # of neutrons

1. use the periodic table to complete the following table:

*assume all atoms are electrically neutral.

element name	atomic number	number of protons	number of electrons
	14
		82
sodium (na)
	12

1. use the periodic table to fill out the following table for the following isotopes.

isotope name	nuclear notation	number of protons	atomic number	number of neutrons	mass number
	$\ce{^{16}_{7}n}$				16
bromine-82	$\ce{^{82}_{35}br}$
he-3			2
	$\ce{^{109}_{47}ag}$				109
uranium-235			92
	$\ce{^{58}_{27}co}$	27

1. isotopes are elements that have the same number of protons, but a different mass because they have a different number of

Explanation:

Question 1

To determine what defines an element, we use the concept that the atomic number (number of protons) is unique to each element. Electrons can change (ionization), and neutrons change for isotopes, but protons determine the element. So the number of protons determines the element.

Step 1: Recall Atomic Structure Rules

• Atomic Number = Number of Protons.
• For neutral atoms, Number of Electrons = Number of Protons.
• Use periodic table knowledge:
• Helium (He): Atomic number is 2. So protons = 2, electrons = 2 (neutral).
• Atomic number 14: Element is Silicon (Si). Protons = 14, electrons = 14.
• Protons = 82: Element is Lead (Pb). Atomic number = 82, electrons = 82.
• Sodium (Na): Atomic number 11. Protons = 11, electrons = 11.
• Atomic number 12: Element is Magnesium (Mg). Protons = 12, electrons = 12.

Step 2: Fill the Table

Element Name	Atomic Number	Number of Protons	Number of Electrons
Silicon (Si)	14	14	14
Lead (Pb)	82	82	82
Sodium (Na)	11	11	11
Magnesium (Mg)	12	12	12

Step 1: Recall Isotope and Nuclear Notation Rules

• Nuclear Notation: $\ce{^A_Z X}$, where \( A \) = Mass Number, \( Z \) = Atomic Number (Protons), Neutrons = \( A - Z \).
• For neutral atoms (here isotopes, neutral unless stated), Electrons = Protons (but table here focuses on protons, neutrons, mass).

Step 2: Calculate for Each Isotope

1. Carbon-14: \( Z = 6 \), \( A = 14 \). Neutrons = \( 14 - 6 = 8 \). Nuclear Notation: $\ce{^{14}_6 C}$.
2. $\ce{^{16}_7 N}$: \( Z = 7 \) (protons), \( A = 16 \). Neutrons = \( 16 - 7 = 9 \). Isotope name: Nitrogen-16.
3. Bromine-82 ($\ce{^{82}_{35} Br}$): \( Z = 35 \) (protons), \( A = 82 \). Neutrons = \( 82 - 35 = 47 \).
4. He-3: \( Z = 2 \) (protons), \( A = 3 \). Neutrons = \( 3 - 2 = 1 \). Nuclear Notation: $\ce{^3_2 He}$.
5. $\ce{^{109}_{47} Ag}$: \( Z = 47 \) (protons), \( A = 109 \). Neutrons = \( 109 - 47 = 62 \). Isotope name: Silver-109.
6. Uranium-235: \( Z = 92 \) (protons), \( A = 235 \). Neutrons = \( 235 - 92 = 143 \). Nuclear Notation: $\ce{^{235}_{92} U}$.
7. $\ce{^{58}_{27} Co}$: \( Z = 27 \) (protons), \( A = 58 \). Neutrons = \( 58 - 27 = 31 \). Isotope name: Cobalt-58.

Step 3: Fill the Table

Isotope Name	Nuclear Notation	Number of Protons	Atomic Number	Number of Neutrons	Mass Number
Nitrogen-16	$\ce{^{16}_7 N}$	7	7	9	16
Bromine-82	$\ce{^{82}_{35} Br}$	35	35	47	82
He-3	$\ce{^3_2 He}$	2	2	1	3
Silver-109	$\ce{^{109}_{47} Ag}$	47	47	62	109
Uranium-235	$\ce{^{235}_{92} U}$	92	92	143	235
Cobalt-58	$\ce{^{58}_{27} Co}$	27	27	31	58

Answer:

a. The # of Protons

Question 2