Give the name of each of the following elements: a. Noble gas in Period 2 b. Halogen in Period 2 c. Alkali metal in Period 3 d. Halogen in Period 4 e. Alkaline-earth metal in Period 4 Q7. A neutral atom has a mass number of 107 and has 61 neutrons. Write its complete nuclear symbol. Q8. An atom has two more protons and two more electrons than the atom in question 7. What is its complete nuclear symbol?
The Correct Answer and Explanation is:
: Give the name of each of the following elements:
a. Noble gas in Period 2 → Neon (Ne)
b. Halogen in Period 2 → Fluorine (F)
c. Alkali metal in Period 3 → Sodium (Na)
d. Halogen in Period 4 → Bromine (Br)
e. Alkaline-earth metal in Period 4 → Calcium (Ca)
Q7: A neutral atom has a mass number of 107 and has 61 neutrons. Write its complete nuclear symbol.
Step 1: Calculate the number of protons.
Mass number = Protons + Neutrons
So, Protons = 107 − 61 = 46
Step 2: Use the periodic table.
An element with atomic number 46 is Palladium (Pd).
Answer:
ⁱ⁰⁷₄₆Pd
Q8: An atom has two more protons and two more electrons than the atom in question 7. What is its complete nuclear symbol?
Step 1: Increase protons to 46 + 2 = 48
Atomic number 48 corresponds to Cadmium (Cd)
Step 2: Assume same number of neutrons (61)
So, mass number = 48 + 61 = 109
Answer:
¹⁰⁹₄₈Cd
Textbook-style Explanation (300 words):
The periodic table is arranged in periods (horizontal rows) and groups (vertical columns) based on atomic structure. Elements are classified into families such as noble gases, halogens, alkali metals, and alkaline-earth metals.
Neon (Ne) is the noble gas found in Period 2. Noble gases are chemically inert due to their full outer electron shells. Fluorine (F) is the halogen in the same period. Halogens are highly reactive nonmetals, especially with alkali metals. Sodium (Na) is the alkali metal in Period 3. Alkali metals are very reactive and have one electron in their outer shell. Bromine (Br), a halogen in Period 4, is a reactive nonmetal known for its use in disinfectants. Calcium (Ca) is the alkaline-earth metal in Period 4, essential for biological functions like muscle contraction.
To determine an element’s nuclear symbol, we use the format:
⁽mass number⁾₍atomic number₎Element symbol
For example, if an atom has a mass number of 107 and 61 neutrons, subtracting gives 46 protons. Atomic number 46 corresponds to palladium (Pd), so the symbol is ⁱ⁰⁷₄₆Pd.
If a new atom has two more protons and electrons, its atomic number is 48. The element with atomic number 48 is cadmium (Cd). Assuming the number of neutrons remains the same, the mass number becomes 48 + 61 = 109, yielding the nuclear symbol ¹⁰⁹₄₈Cd.
This exercise illustrates how atomic structure determines an element’s identity and how nuclear symbols represent key atomic data.
