QCM : Periodic Table and Bonding Fundamentals — 12 questions

Explication

The structure of the periodic table is organized primarily by atomic number, with elements arranged in periods (rows) and groups (columns). This organization reflects periodic trends in properties and reactivity, making option 0 the correct description.

Explication

The Bohr model and the electron shells pattern described in the content state that shells are filled in the order 2, 8, 8..., which reflects the maximum number of electrons each shell can hold in the simplified model. This pattern is fundamental to understanding atomic structure and is explicitly mentioned in the source content.

Explication

Valence electrons are located in the outermost shell of an atom and are involved in chemical bonding. They determine how an atom reacts with others and form the basis for chemical properties and reactivity.

Explication

Henry Moseley's work in 1913 established the relationship between atomic number and element identity, leading to the modern periodic table organized by atomic number.

Explication

Alkali metals become more reactive down their group because their outer electrons are farther from the nucleus and easier to lose, while halogens become more reactive up their group because smaller atoms more readily gain electrons to complete their outer shells. This contrasting trend is explicitly supported by the course content, which states that reactivity increases down the group for alkali metals and up the group for halogens.

Explication

Svante Arrhenius is credited with proposing the concept of ion formation in 1884, explaining how substances dissolve in water to produce charged particles called ions, which are essential for understanding electrolysis and conductivity in solutions.

Explication

The formation of ionic compounds is caused by the transfer of electrons from metals to non-metals, which leads to the creation of ions that attract each other electrostatically, forming ionic bonds.

Explication

Understanding covalent bonding involves analyzing how atoms share electrons to fill their valence shells, which directly predicts which molecules can form through covalent bonds. The other options relate to ionic bonding or nuclear properties, which are not directly about covalent sharing.

Explication

Diatomic elements are characterized by existing as molecules consisting of two atoms in their standard state, such as O₂ and N₂. This molecular form is their defining feature, unlike the other options which describe physical states or bonding types that are not exclusive or defining for diatomic elements.

Explication

A synthesis reaction involves two or more substances combining to form a single product, as described in the course content. The other options describe decomposition, displacement, and neutralisation reactions, respectively.

Explication

Adjusting coefficients in a chemical equation is done to ensure that the number of each type of atom is the same on both sides of the equation, reflecting the law of conservation of mass. This process does not change chemical formulas, increase molecule count arbitrarily, or serve only aesthetic purposes.

Explication

Indicators are substances that change colour depending on the pH of the solution, allowing us to identify whether the solution is acidic, neutral, or alkaline.