Question

Which pair of clcments belong to the same group? (1) Elements with atomic number 17 and 38 (2) Elements with atomic number 20 and 40 (3) Elements with atomic number 17 and 53 (4) Elements with atomic number 11 and 53

Short answer

Pair (3): Elements with atomic numbers 17 (Chlorine) and 53 (Iodine).

Step-by-step solution

- Identify Elements by Atomic Number

Determine the chemical elements corresponding to the given atomic numbers using the periodic table.(1) Atomic number 17: Chlorine (Cl) Atomic number 38: Strontium (Sr) (2) Atomic number 20: Calcium (Ca) Atomic number 40: Zirconium (Zr) (3) Atomic number 17: Chlorine (Cl) Atomic number 53: Iodine (I) (4) Atomic number 11: Sodium (Na) Atomic number 53: Iodine (I)

- Determine Groups of Each Element

Using the periodic table, find the group numbers for each element:(1) Chlorine (Cl) - Group 17, Strontium (Sr) - Group 2(2) Calcium (Ca) - Group 2, Zirconium (Zr) - Group 4(3) Chlorine (Cl) - Group 17, Iodine (I) - Group 17(4) Sodium (Na) - Group 1, Iodine (I) - Group 17

- Compare Groups to Find Elements in the Same Group

Compare the groups for each pair of elements to identify which pair has elements in the same group:(1) Different groups (17 and 2)(2) Different groups (2 and 4)(3) Same group (17 and 17)(4) Different groups (1 and 17)

- Confirm the Correct Answer

Review the comparisons: Pair (3) with elements Chlorine (Cl) and Iodine (I) both belong to Group 17, confirming they are in the same group.

Key concepts

Atomic Number

The atomic number is a fundamental concept in chemistry. It represents the number of protons found in the nucleus of an atom. The atomic number uniquely identifies a chemical element.
You can find the atomic number of an element in the periodic table. It is usually placed above the elemental symbol.
For example:

• Chlorine (Cl) has an atomic number of 17.
• Sodium (Na) has an atomic number of 11.

The higher the atomic number, the more protons the atom has. This number also determines the element's position in the periodic table. Each element increases by one atomic number as you move horizontally from left to right across a period.
Knowing the atomic number helps to identify the element and provides important information regarding its chemical behavior.

Chemical Elements

Chemical elements are the simplest types of substances made up of only one kind of atom. Each chemical element is unique and represented by a symbol, such as H for Hydrogen or O for Oxygen.
Elements are organized in the periodic table. Each element has atoms with the same number of protons, known as the atomic number. For instance:

• Chlorine (Cl) with an atomic number of 17
• Calcium (Ca) with an atomic number of 20

Each element behaves differently in chemical reactions due to its atomic structure. This uniqueness is what makes chemistry so diverse and fascinating.
There are over 100 known elements, and they combine in various ways to form all substances known to us. Elements are essential building blocks of matter, which means understanding them is key to understanding chemistry and the world around us.

Periodic Table

The periodic table is a systematic arrangement of chemical elements in rows and columns. It organizes elements based on their atomic number, electron configurations, and recurring chemical properties.
The periodic table helps predict the properties of elements and their compounds. Key features include:

• Rows called periods
• Columns called groups or families
• Elements in the same group share similar chemical properties

For example, elements with atomic numbers 17 (Chlorine, Cl) and 53 (Iodine, I) are in Group 17. This means they are in the same group and share similar properties, such as being halogens. Halogens are known for their reactivity and ability to form salts when combined with metals.
Understanding the periodic table is crucial for studying chemistry because it provides a framework for understanding how elements interact and behave.