Which is the electron configuration for lithium?

1s2

2s3

What is the oxidation number of the element n in the compound n2o5? 1. 3 2. 6 3. 5 4. 2 5. - 6 6. 4 7. - 2 8. - 3 9. - 5 10. - 4?

What are the mole fraction and the mass percent of a solution made by dissolving 6.77 g of KI in 0.400 L of water (d = 1.00 g/mL) ?

If Uranium-240 emits an alpha particle, what does it transmutate into? A) Thorium - 236 B) Thorium-238 C) Plutonium-244 D) Uranium-235

Consider the combustion reaction, 2C4H2+5O 2--->4 CO2+2H2O where C2 H2 Hf = 227.4 kJ/mol), CO2 (Hf = - 393.5 kJ/mol), and H2 O (Hf = - 241.82 kJ/mol). What is the enthalpy of the reaction? -2,512.4 kJ -1,256.2 kJ 1,256.2 kJ 2,512.4 kJ

Which is a better conductor of heat: air or a copper wire? Why?

What is the percent by mass of solute if 14.60g 74.95g of water?

7 An atom that has 13 protons and 15 neutrons is an isotope of the element (1) nickel (3) aluminum (2) silicon (4) phosphorus

The graph below shows how solubility changes with temperature. What is the solubility of Na2HAsO4 at 60°C? 20 g/100 mL of water 46 g/100 mL of water 65 g/100 mL of water 70 g/100 mL of water

Which statement regarding water is true? Energy must be given off in order to break down the crystal lattice of ice to a liquid. Hydrogen bonds are stronger than covalent bonds. Liquid water is less dense than solid water.

Which of the following elements has the fewest valence electrons?. a. beryllium. b. boron. c. carbon. d. lithium