Some students are using samples of different substances for a lab investigation. They plan to observe the physical properties of each substance and record their observations in a table like the one below. Which of the substances observed are elements?

Element R and Element Q have the same number of valence electrons. These elements both have similar chemical behavior, but Element R has fewer energy levels than Element Q. Which statement best describes the positions of the two elements in the periodic table?

A student obtains two strips of magnesium, Mg, ribbon that are each 3 cm long. One strip of magnesium is placed in a test tube containing 5 mL of water, and the other strip is placed in a test tube containing 5 mL of hydrochloric acid, HCl. Both liquids are at room temperature. The student’s observations are recorded in the table. Which statement is not supported by the student’s observations?

What is the difference between the number of electrons in an atom of selenium, Se, and the number of electrons in an atom of aluminum, Al?

Four students were given a list of compounds and asked to identify which ones are organic. Which student correctly identified the organic compounds in the list?