Question

Which one of the following statements about atomic number is false? (1) It is equal to the number of protons present in the nucleus. (2) It is a more fundamental property of the atom than the atomic weight. (3) No two elements can have the same atomic number. (4) The atomic number of an element decides its stability.

Short answer

Statement 4 is false: 'The atomic number of an element decides its stability.'

Step-by-step solution

Understand the Atomic Number Concept

The atomic number is defined as the number of protons present in the nucleus of an atom. This property is fundamental for the identity and classification of elements in the periodic table.

Analyze Statement 1

Statement 1: 'It is equal to the number of protons present in the nucleus.' This is a true statement because the atomic number directly represents the count of protons in an atom's nucleus.

Analyze Statement 2

Statement 2: 'It is a more fundamental property of the atom than the atomic weight.' This is also true because atomic number determines the element's identity, while atomic weight can vary with isotopes.

Analyze Statement 3

Statement 3: 'No two elements can have the same atomic number.' This is true. Each element on the periodic table has a unique atomic number, distinguishing it from all other elements.

Analyze Statement 4

Statement 4: 'The atomic number of an element decides its stability.' This is false. The stability of an atom generally depends on the neutron-to-proton ratio, not purely on its atomic number.

Conclude the False Statement

Based on the analysis, the false statement is statement 4: 'The atomic number of an element decides its stability.'

Key concepts

number of protons

The atomic number of an element is fundamentally important because it equals the number of protons in an atom's nucleus. This number is unique to each element and is always a whole number. For example, hydrogen has an atomic number of 1, meaning it has one proton in its nucleus. Oxygen has an atomic number of 8, indicating it has eight protons.

Protons are positively charged particles, and their number not only defines the element but also determines its place in the periodic table. The chemical behavior of an atom is influenced by its atomic number, as it affects how atoms interact with each other.

Knowing the number of protons helps in predicting the physical and chemical properties of an element. By referring to the periodic table, you can identify the number of protons for any element, giving you a better understanding of its characteristics.

• Each proton carries a positive electric charge (+1).
• The number of protons determines the atomic number (Z) of an element.
• Protons are found in the nucleus, along with neutrons.

element identity

The identity of an element is determined by its atomic number, which is the number of protons in the nucleus. Each element on the periodic table has a unique atomic number, and no two different elements share the same number of protons.

For instance, carbon always has an atomic number of 6. This means that any atom with 6 protons is a carbon atom, regardless of the number of neutrons or electrons. As such, the atomic number is a critical identifier.

Changes in the number of protons result in a different element. This is why atomic number is often referred to as the most fundamental property of an atom.
The sequence of elements in the periodic table follows increasing atomic numbers, not atomic weights.

• Elements are classified based on their atomic number.
• Hydrogen (atomic number 1) is always the first element, followed by helium (atomic number 2).
• The atomic number provides a straightforward way to understand and categorize elements.

atomic stability

Atomic stability is generally determined by the ratio of neutrons to protons in the nucleus. While the atomic number indicates the number of protons, the number of neutrons can vary, resulting in different isotopes of the same element.

For example, Carbon-12 has 6 protons and 6 neutrons, while Carbon-14 has 6 protons and 8 neutrons. Both are carbon, but Carbon-14 is radioactive and less stable.

Stability is crucial for understanding an element's behavior in reactions and its occurrence in nature. Stable elements are more likely to be found in their native form, while unstable isotopes may undergo radioactive decay.

• A balanced neutron-to-proton ratio contributes to atomic stability.
• Isotopes of the same element can have different stability levels.
• Stable atoms have a good balance of protons and neutrons.

periodic table

The periodic table is a systematic arrangement of all known elements based on their atomic number, electronic configuration, and recurring chemical properties. Each element is placed in a specific location according to its atomic number.

The table is divided into periods (rows) and groups (columns). Elements in the same group often exhibit similar chemical behaviors because they have the same number of electrons in their outer shell. For instance, all elements in Group 1 are alkali metals and share similar reactive properties.

• The periodic table organizes elements by increasing atomic numbers.
• Groups and periods help predict element properties.
• Elements like gold (Au) and silver (Ag) are found in specific groups based on shared traits.

The periodic table is essential for studying chemistry as it highlights trends and patterns in elemental properties, aiding in the prediction of chemical reactions and the understanding of atomic structure.