Question

1. fill in the following chart: (assume all atoms are electrically neutral.)

element symbol	atomic number	mass number	# of protons	# of neutrons	# of electrons
	13			14
		31	15
				20	19
br		80
	30	65
			82	125
		128			52
	44			58
hg		198
			55	78

Explanation:

Step1: Recall atomic - related rules

For a neutral atom, the atomic number is equal to the number of protons and the number of electrons. The mass number is the sum of the number of protons and neutrons.

Step2: First row (Oxygen)

The atomic number of oxygen (O) is 8. Since it is neutral, the number of protons = 8 and the number of electrons = 8. The number of neutrons = mass number - number of protons = 16 - 8 = 8.

Step3: Second row

The atomic number is 13. So the element symbol is Al (aluminum). The number of protons = 13. Since it is neutral, the number of electrons = 13. The mass number = number of protons+number of neutrons = 13 + 14 = 27.

Step4: Third row

The number of protons is 15, so the element is P (phosphorus). The atomic number = 15. Since it is neutral, the number of electrons = 15. The number of neutrons = mass number - number of protons = 31 - 15 = 16.

Step5: Fourth row

The number of electrons is 19, so the number of protons is 19 (since it is neutral), and the atomic number is 19. The element is K (potassium). The mass number = number of protons+number of neutrons = 19+20 = 39.

Step6: Fifth row

The element symbol is Br (bromine). The atomic number of bromine is 35. So the number of protons = 35. Since it is neutral, the number of electrons = 35. The number of neutrons = mass number - number of protons = 80 - 35 = 45.

Step7: Sixth row

The atomic number is 30, so the element is Zn (zinc). The number of protons = 30. Since it is neutral, the number of electrons = 30. The number of neutrons = mass number - number of protons = 65 - 30 = 35.

Step8: Seventh row

The number of protons is 82, so the element is Pb (lead). The atomic number = 82. Since it is neutral, the number of electrons = 82. The mass number = number of protons+number of neutrons = 82 + 125 = 207.

Step9: Eighth row

The number of electrons is 52, so the number of protons is 52 (since it is neutral), and the atomic number is 52. The element is Te (tellurium). The number of neutrons = mass number - number of protons = 128 - 52 = 76.

Step10: Ninth row

The atomic number is 44, so the element is Ru (ruthenium). The number of protons = 44. Since it is neutral, the number of electrons = 44. The mass number = number of protons+number of neutrons = 44+58 = 102.

Step11: Tenth row

The element symbol is Hg (mercury). The atomic number of mercury is 80. So the number of protons = 80. Since it is neutral, the number of electrons = 80. The number of neutrons = mass number - number of protons = 198 - 80 = 118.

Step12: Eleventh row

The number of protons is 55, so the element is Cs (cesium). The atomic number = 55. Since it is neutral, the number of electrons = 55. The mass number = number of protons+number of neutrons = 55 + 78 = 133.

Answer:

Element symbol	Atomic number	Mass number	# of protons	# of neutrons	# of electrons
Al	13	27	13	14	13
P	15	31	15	16	15
K	19	39	19	20	19
Br	35	80	35	45	35
Zn	30	65	30	35	30
Pb	82	207	82	125	82
Te	52	128	52	76	52
Ru	44	102	44	58	44
Hg	80	198	80	118	80
Cs	55	133	55	78	55