Question

periodic table practice: use a periodic table to answer the following questions about each element. fill in each blank with the correct information.
open - ended questions: answer the following questions in complete sentences.

1. explain the difference between an element and a compound.
2. describe what a mixture is and give an example from everyday life.
3. why is the periodic table important for scientists?
4. in your own words, explain the difference between atomic mass and atomic number.
5. how does the position of an element on the periodic table relate to its reactivity?

Explanation:

• Question 15: An element is a pure substance made of only one type of atom. A compound is a pure substance formed when two or more different elements chemically combine in a fixed ratio. For example, oxygen (\(O_2\)) is an element (made of only oxygen atoms), while water (\(H_2O\)) is a compound (made of hydrogen and oxygen atoms in a 2:1 ratio).
• Question 16: A mixture is a combination of two or more substances (elements or compounds) that are not chemically combined. In a mixture, the substances retain their individual properties. An everyday example is air, which is a mixture of nitrogen (\(N_2\)), oxygen (\(O_2\)), carbon dioxide (\(CO_2\)), and other gases. Each gas in air keeps its own properties.
• Question 17: The Periodic Table is important for scientists because it organizes elements based on their atomic number, electron configuration, and recurring chemical properties. Scientists can predict an element's properties (such as reactivity, physical state, etc.) based on its position in the table. It also helps in understanding trends (like atomic size, ionization energy) across periods and groups.
• Question 18: Atomic number is the number of protons in the nucleus of an atom. It defines the identity of an element (e.g., carbon has an atomic number of 6, so any atom with 6 protons is carbon). Atomic mass is the average mass of an atom of an element, taking into account the different isotopes (atoms of the same element with different numbers of neutrons). For example, carbon - 12 has a mass of approximately 12 atomic mass units, and carbon - 13 has a mass of approximately 13 atomic mass units, and the atomic mass of carbon is a weighted average of its isotopes.
• Question 19: In the Periodic Table, for metals (on the left side and in the middle), reactivity generally increases down a group (as the outermost electrons are further from the nucleus and easier to lose) and decreases across a period (as the effective nuclear charge increases, making it harder to lose electrons). For non - metals (on the right side), reactivity generally increases across a period (as they gain electrons more easily due to increasing effective nuclear charge) and decreases down a group (as the outermost energy level is further from the nucleus, making it harder to gain electrons).

Answer:

• 15. An element consists of one type of atom; a compound is a chemical combination of different elements.
• 16. A mixture combines substances without chemical bonding (e.g., air).
• 17. It organizes elements for property prediction and trend understanding.
• 18. Atomic number: number of protons (element identity); atomic mass: average atomic mass (isotope - weighted).
• 19. Metal reactivity: up - group increase, across - period decrease. Non - metal reactivity: across - period increase, down - group decrease.