For a1, its atomic number is 13 and its mass number is 27 how many neutrons does it have?

Helium and hydrogen have almost the same atomic size, yet the ionization energy of helium is almost twice that of hydrogen. explain why hydrogen has a much higher ionization energy than any element in group 1 does.

A gas under an initial pressure of 0.60 atm is compressed at constant temperature from 27 L to 3.0 L. The final pressure becomes

skid marks about 6.7 km long. If the car had an initial speed of 425 km/h, estimate the coefficient of kinetic friction. The acceleration of gravity is 9.81 m/s 2.

What is the melting temperature of magnesium in kelvin

Where are the electrons located on a periodic table?

Periodic table, chemistry questions who discovered lanthanides. how did they discover it, when did they discover it.

A flask containing 155cm^3 of hydrogen was collected under a pressure of 22.5kPa. What pressure would have been required in order for the volume of the gas to have been 90.0 cm^3 at constant temperature?

Which change is most likely to occur when a molecule of H2 and a molecule of I2 collide with proper orientation and sufficient energy? 1. a chemical change, because a compound is formed 2. a chemical change, because an element is formed 3.

Which substance is a diatomic molecule? a. he b. o2 c. co2 d. h2o?

What is the difference between the electronegativity values of sodium and bromine?