Question

name of element | element symbol | mass number | atomic number | protons | neutrons | electrons
boron | b | 11 | 5 | 5 | 6 | 5
sodium | na | marked | 11 | 11 | 12 | 11
yttrium | y | 89 | 39 | 39 | 50 | 39
copper | cu | | 29 | | 35 |

tc	98		43
pb	207

thallium | | 204 | 81 | | |

h

0

carbon | | 12 | | | |

n			7
ba					56

calcium | | | | | |

si

14

argon | | | 18 | | |

mg

12

12

Answer:

To solve for the missing values in the table, we use the following relationships in atomic structure:

• Atomic Number (Z) = Number of Protons = Number of Electrons (in a neutral atom).
• Mass Number (A) = Number of Protons + Number of Neutrons.

1. Sodium (Na)

• Atomic Number (\( Z \)) = 11 (given Protons = 11).
• Mass Number (\( A \)) = Protons + Neutrons = \( 11 + 12 = 23 \) (matches the obscured value).

2. Yttrium (Y)

• Atomic Number (\( Z \)) = 39 (given Protons = 39) → Electrons = 39 (neutral atom).
• Mass Number (\( A \)) = 89 (given) → Neutrons = \( 89 - 39 = 50 \) (matches).

3. Copper (Cu)

• Atomic Number (\( Z \)) = 29 (given) → Protons = 29, Electrons = 29.
• Neutrons = 35 (given) → Mass Number = \( 29 + 35 = 64 \).

4. Technetium (Tc)

• Atomic Number (\( Z \)) = 43 (given Protons = 43) → Electrons = 43.
• Mass Number (\( A \)) = 98 (given) → Neutrons = \( 98 - 43 = 55 \).

5. Lead (Pb)

• Atomic Number (\( Z \)) = 82 (atomic number of Pb) → Protons = 82, Electrons = 82.
• Mass Number (\( A \)) = 207 (given) → Neutrons = \( 207 - 82 = 125 \).

6. Thallium (Tl)

• Atomic Number (\( Z \)) = 81 (given) → Protons = 81, Electrons = 81.
• Mass Number (\( A \)) = 204 (given) → Neutrons = \( 204 - 81 = 123 \).

7. Hydrogen (H)

• Atomic Number (\( Z \)) = 1 (atomic number of H) → Protons = 1, Electrons = 1.
• Neutrons = 0 (given) → Mass Number = \( 1 + 0 = 1 \).

8. Carbon (C)

• Atomic Number (\( Z \)) = 6 (atomic number of C) → Protons = 6, Electrons = 6.
• Mass Number (\( A \)) = 12 (given) → Neutrons = \( 12 - 6 = 6 \).

9. Nitrogen (N)

• Atomic Number (\( Z \)) = 7 (given Protons = 7) → Electrons = 7.
• Mass Number (\( A \)): Typical mass number for N is 14 (most common isotope) → Neutrons = \( 14 - 7 = 7 \).

10. Barium (Ba)

• Atomic Number (\( Z \)) = 56 (given Electrons = 56) → Protons = 56.
• Mass Number (\( A \)): Typical mass number for Ba is 137 (most common isotope) → Neutrons = \( 137 - 56 = 81 \).

11. Calcium (Ca)

• Atomic Number (\( Z \)) = 20 (atomic number of Ca) → Protons = 20, Electrons = 20.
• Mass Number (\( A \)): Typical mass number for Ca is 40 → Neutrons = \( 40 - 20 = 20 \).

12. Silicon (Si)

• Atomic Number (\( Z \)) = 14 (given Electrons = 14) → Protons = 14.
• Mass Number (\( A \)): Typical mass number for Si is 28 → Neutrons = \( 28 - 14 = 14 \).

13. Argon (Ar)

• Atomic Number (\( Z \)) = 18 (given) → Protons = 18, Electrons = 18.
• Mass Number (\( A \)): Typical mass number for Ar is 40 → Neutrons = \( 40 - 18 = 22 \).

14. Magnesium (Mg)

• Atomic Number (\( Z \)) = 12 (given Protons = 12) → Electrons = 12.
• Mass Number (\( A \)): Typical mass number for Mg is 24 → Neutrons = \( 24 - 12 = 12 \).

Filled Table (Key Values):

Name	Symbol	Mass Number	Atomic Number	Protons	Neutrons	Electrons
Sodium	Na	23	11	11	12	11
Yttrium	Y	89	39	39	50	39
Copper	Cu	64	29	29	35	29
Technetium	Tc	98	43	43	55	43
Lead	Pb	207	82	82	125	82
Thallium	Tl	204	81	81	123	81
Hydrogen	H	1	1	1	0	1
Carbon	C	12	6	6	6	6
Nitrogen	N	14	7	7	7	7
Barium	Ba	137	56	56	81	56
Calcium	Ca	40	20	20	20	20
Silicon	Si	28	14	14	14	14
Argon	Ar	40	18	18	22	18
Magnesium	Mg	24	12	12	12	12

(Note: For isotopes, mass numbers may vary, but the above uses the most common stable isotopes.)