atomic structure & periodic table (1–25)
1. a neutral atom has 14 protons. how many electrons does it have?
a. 12
b. 13
c. 14
d. 28
2. an element has atomic mass 35 and atomic number 17. how many neutrons?
a. 17
b. 18
c. 35
d. 52
3. which scientist proved the atom is mostly empty space?
a. dalton
b. thomson
c. rutherford
d. democritus
4. if an atom has 8 protons and 8 neutrons, what is its atomic mass?
a. 8
b. 16
c. 24
d. 64
5. why are electrons ignored in atomic mass calculations?
a. they move too fast
b. they are negative
c. they have almost no mass
d. they orbit outside the atom
6. an atom gains two electrons. what happens to its charge?
a. becomes +2
b. becomes +1
c. becomes -1
d. becomes -2
7. which change will turn a neutral atom into an ion?
a. losing neutrons
b. gaining or losing electrons
c. gaining protons
d. changing energy levels
8. if the atomic number is 20, how many electrons are present?
a. 10
b. 18
c. 20
d. 40
9. why are atoms electrically neutral?
a. protons cancel neutrons
b. electrons cancel mass
c. protons equal electrons
d. neutrons equal protons
10. valence electrons are found in the —
a. nucleus
b. innermost shell
c. outermost shell
d. electron cloud
11. which family has one valence electron and is highly reactive?
a. halogens
b. noble gases
c. alkali metals
d. chalcogens
12. which family has 7 valence electrons?
a. halogens
b. alkali metals
c. noble gases
d. transition metals
13. why are noble gases chemically stable?
a. they have no protons
b. they have low mass
c. they have full valence shells
d. they have no neutrons

Question

atomic structure & periodic table (1–25)
1. a neutral atom has 14 protons. how many electrons does it have?
   a. 12
   b. 13
   c. 14
   d. 28
2. an element has atomic mass 35 and atomic number 17. how many neutrons?
   a. 17
   b. 18
   c. 35
   d. 52
3. which scientist proved the atom is mostly empty space?
   a. dalton
   b. thomson
   c. rutherford
   d. democritus
4. if an atom has 8 protons and 8 neutrons, what is its atomic mass?
   a. 8
   b. 16
   c. 24
   d. 64
5. why are electrons ignored in atomic mass calculations?
   a. they move too fast
   b. they are negative
   c. they have almost no mass
   d. they orbit outside the atom
6. an atom gains two electrons. what happens to its charge?
   a. becomes +2
   b. becomes +1
   c. becomes -1
   d. becomes -2
7. which change will turn a neutral atom into an ion?
   a. losing neutrons
   b. gaining or losing electrons
   c. gaining protons
   d. changing energy levels
8. if the atomic number is 20, how many electrons are present?
   a. 10
   b. 18
   c. 20
   d. 40
9. why are atoms electrically neutral?
   a. protons cancel neutrons
   b. electrons cancel mass
   c. protons equal electrons
   d. neutrons equal protons
10. valence electrons are found in the —
    a. nucleus
    b. innermost shell
    c. outermost shell
    d. electron cloud
11. which family has one valence electron and is highly reactive?
    a. halogens
    b. noble gases
    c. alkali metals
    d. chalcogens
12. which family has 7 valence electrons?
    a. halogens
    b. alkali metals
    c. noble gases
    d. transition metals
13. why are noble gases chemically stable?
    a. they have no protons
    b. they have low mass
    c. they have full valence shells
    d. they have no neutrons

Accepted Answer

### Question 1
# Explanation:
## Step1: Recall neutral atom electron-proton relation
A neutral atom has equal number of electrons and protons.
## Step2: Determine number of electrons
Given 14 protons, so electrons = 14.
# Answer: C. 14

### Question 2
# Explanation:
## Step1: Recall atomic mass formula
Atomic mass = number of protons + number of neutrons. Atomic number = number of protons.
## Step2: Calculate number of neutrons
Atomic number = 17 (protons), atomic mass = 35. Neutrons = 35 - 17 = 18.
# Answer: B. 18

### Question 3
# Brief Explanations:
Rutherford's gold foil experiment proved the atom is mostly empty space. Dalton proposed atomic theory, Thomson discovered electrons, Democritus proposed atom concept.
# Answer: C. Rutherford

### Question 4
# Explanation:
## Step1: Recall atomic mass calculation
Atomic mass = protons + neutrons.
## Step2: Calculate atomic mass
Protons = 8, neutrons = 8. Atomic mass = 8 + 8 = 16.
# Answer: B. 16

### Question 5
# Brief Explanations:
Electrons have almost no mass (mass of electron is about 1/1836 of proton/neutron), so ignored in atomic mass. Other options are incorrect (movement, charge, orbit don't relate to mass ignoring).
# Answer: C. They have almost no mass

### Question 6
# Explanation:
## Step1: Recall electron charge
Each electron has a charge of -1.
## Step2: Determine charge change
Gaining 2 electrons: charge becomes 0 + (-2) = -2.
# Answer: D. Becomes -2

### Question 7
# Brief Explanations:
Ions are formed by gaining or losing electrons (changes charge). Neutrons don't affect charge, gaining protons changes element, energy levels don't form ions.
# Answer: B. Gaining or losing electrons

### Question 8
# Explanation:
## Step1: Recall neutral atom electron-proton relation
Atomic number = number of protons = number of electrons in neutral atom.
## Step2: Determine number of electrons
Atomic number = 20, so electrons = 20.
# Answer: C. 20

### Question 9
# Brief Explanations:
Atoms are neutral because number of protons (positive charge) equals number of electrons (negative charge), so charges cancel. Protons don't cancel neutrons, electrons don't cancel mass, neutrons ≠ protons usually.
# Answer: C. Protons equal electrons

### Question 10
# Brief Explanations:
Valence electrons are in the outermost shell (involved in bonding). Nucleus has protons/neutrons, innermost shell has core electrons, electron cloud is general, but valence is outermost.
# Answer: C. outermost shell

### Question 11
# Brief Explanations:
Alkali metals (Group 1) have 1 valence electron and are highly reactive. Halogens have 7, noble gases have 8 (stable), chalcogens have 6.
# Answer: C. Alkali metals

### Question 12
# Brief Explanations:
Halogens (Group 17) have 7 valence electrons. Alkali metals have 1, noble gases have 8, transition metals have variable.
# Answer: A. Halogens

### Question 13
# Brief Explanations:
Noble gases have full valence shells (8 electrons, or 2 for He), making them stable. They have protons/neutrons, mass and neutrons don't relate to stability.
# Answer: C. They have full valence shells

Sovi.AI - AI Math Tutor

QUESTION IMAGE

Question

Explanation:

Question 1

Step1: Recall neutral atom electron-proton relation

Step2: Determine number of electrons

Step1: Recall atomic mass formula

Step2: Calculate number of neutrons

Answer:

Question 2