A)state the number of valence electrons for the element o? b) an element with 5 protons, has how many electrons? c) if an element has 4 electrons and an atomic mass of 9, what element is it? d)chlorine has two naturally occurring isotopes: cl-35 and cl-37. which isotope is more abundant if the atomic mass of chlorine is 35.45?

Calculate the number of molecules present in 0.750 mol of mgo.

Calculate the standard enthalpy of formation of liquid methanol, ch3oh(l), using the following information: c(graphite) + o2 latex: \longrightarrow ⟶ co2(g) latex: \delta δ h° = –393.5 kj/mol h2(g) + o2 latex: \longrightarrow ⟶ h2o(l) latex: \delta δ h° = –285.8 kj/mol ch3oh(l) + o2(g) latex: \longrightarrow ⟶ co2(g) + 2h2o(l) latex: \delta δ h° = –726.4 kj/mol

Select the statement that describe chemical properties a. antacid tablets neutralize stomach acid b. helium is the lightest monatomic element c. water freezes at 0 celsius d. mercury is liquid at room temperature