Elemental chemistry problems and solutions

Question 1: What is an element in chemistry?

Solution: An element in chemistry is a substance that cannot be broken down into simpler substances by chemical reactions. Each element is defined by the number of protons in its atoms, known as its atomic number.

Question 2: What is the atomic number of an element?

Solution: The atomic number of an element is the number of protons in the nucleus of an atom of that element. It defines the chemical properties of the element and its place in the periodic table.

Question 3: What is the difference between a period and a group in the periodic table?

Solution: A period in the periodic table is a horizontal row of elements. A group is a vertical column of elements. Elements in the same group share similar chemical properties.

Question 4: What are isotopes?

Solution: Isotopes are variants of a particular chemical element which differ in neutron number, but have the same number of protons (atomic number). Isotopes of an element have the same atomic number but different mass numbers.

Question 5: What is the chemical formula for water?

Solution: The chemical formula for water is H₂O, which means it consists of two hydrogen atoms and one oxygen atom.

Question 6: What is a cation and an anion?

Solution: A cation is a positively charged ion, resulting from the loss of electrons. An anion is a negatively charged ion, resulting from the gain of electrons.

Question 7: How many protons, electrons and neutrons does the carbon-12 isotope have?

Solution: The carbon-12 isotope has 6 protons, 6 electrons, and 6 neutrons.

Question 8: What does the law of conservation of mass state?

Solution: The law of conservation of mass states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations. The mass of the products in a chemical reaction must equal the mass of the reactants.

Question 9: What is the noble gas configuration?

Solution: The noble gas configuration is an electron configuration in which all electron orbitals are fully filled. It represents a very stable, low-energy configuration. Noble gas configuration is the electron configuration of noble gases, such as helium, neon, argon, krypton, xenon, and radon, which are located in the outermost column of the periodic table.

Question 10: How is the atomic mass of an element calculated?

Solution: The atomic mass of an element is calculated by multiplying the mass of each isotope by its natural abundance, and then adding those values. This value is then usually given in atomic mass units.

Question 11: What is Avogadro’s number?

Solution: Avogadro’s number, also known as Avogadro’s constant, is the number of constituent particles, usually atoms or molecules, in one mole of a given substance. It is approximately 6.022 x 10²³ particles per mole.

Question 12: What is a mole in chemistry?

Solution: A mole in chemistry is the base unit of amount of substance in the International System of Units. It provides a bridge between the atom and the macroscopic world. One mole contains exactly 6.022 x 10²³ elementary entities (atoms, molecules, ions, electrons etc.)

Question 13: What is the heaviest naturally occurring element on Earth?

Solution: The heaviest naturally occurring element on Earth is Uranium (U), with an atomic number of 92.

Question 14: What are transition metals?

Solution: Transition metals are elements that are located in Groups 3 to 12 of the periodic table. These metals share many physical and chemical properties in common, including high melting points, multiple oxidation states, and often the ability to form colored compounds.

Question 15: What is the difference between ionic and covalent bonds?

Solution: Ionic bonds occur when electrons are transferred from one atom to another, resulting in the formation of positive and negative ions. Covalent bonds occur when two atoms share one or more pairs of electrons.

Question 16: What is the chemical formula for table salt?

Solution: The chemical formula for table salt, also known as sodium chloride, is NaCl.

Question 17: What is a polyatomic ion?

Solution: A polyatomic ion is an ion composed of two or more atoms covalently bonded that can be considered as acting as a single unit in the context of acid/base chemistry or in the formation of salts.

Question 18: What are alkali metals?

Solution: Alkali metals are a group of chemical elements from Group 1 of the periodic table (lithium, sodium, potassium, rubidium, cesium, and francium). They are highly reactive and have only one electron in their outermost shell.

Question 19: What is an alloy?

Solution: An alloy is a combination of two or more different metals, or a metal and another element, mixed together to create a new substance with improved properties. For example, steel is an alloy of iron and carbon.

Question 20: What is the atomic mass of hydrogen?

Solution: The atomic mass of hydrogen, the lightest element, is approximately 1.008 atomic mass units (u). This takes into account the natural abundance of its isotopes.

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