I’m confused on how to answer this question somebody me

Write the chemical symbols for three different atoms or atomic cations with 27 electrons. asap!

Calcium hydride (cah2) reacts with water to form hydrogen gas: cah2(s) + 2h2o(l) → ca(oh)2(aq) + 2h2(g) how many grams of cah2 are needed to generate 45.0 l of h2 gas at a pressure of 0.995 atm and a temperature of 32 °c?

Alice did an experiment to find the relationship between the angle at which a ray of light strikes a mirror and the angle at which the mirror reflects the light. she placed a ray box in front of a mirror. she changed the angle at which the light from the ray box struck the mirror and noted the corresponding angle at which the mirror reflected the light. which of the following is the dependent variable in this experiment? the mirror used to reflect the light the ray box used as the source of light angle at which the light from the ray box strikes the mirror angle at which the mirror reflects the light from the ray box