A single atom of an element has 21 neutrons, 20 electrons, and 20 protons. Which element is it?

K

Zr

Ca

Sc

How do forensic scientist determine what exactly everything is

A light microscope would be most advantageous for viewing which of the following? a. small molecule such as water b. a DNA strand c. virus d. eukaryotic cells such as green algae

Which of the following aqueous solutions are good buffer systems?. 0.13 M potassium fluoride + 0.26 M hydrofluoric acid 0.16 M hydrocyanic acid + 0.15 M sodium cyanide 0.25 M hydrobromic acid + 0.20 M potassium bromide 0.30 M acetic acid + 0.

Which statement describes a newton? O It exists only for objects on Earth. It measures the mass of an object It reflects the amount of force an object exerts. It states that every object attracts another object

In a chemical reaction 18 grams of hydrochloride acid reacts with 20 grams of sodium hydroxine to produce sodium chlorine and water which statement is correct?

Which of the following is an incorrect way of rearranging the density formula: a. m=v•d b. V=d/m c. V=m/d d. Both a and b are incorrect

Describe how the periodic table differentiates between metals and nonmetals. I need a very informative description/explanation on this.

When the ideal gas law is arranged as shown below, what property of the gas is being solved for (represented by the X) ? x equals PV over nR

Which element could chlorine bond with to form an ionic compound? helium oxygen fluorine sodium

A scientist conducted one trial experiment and got unexpected results. how can the scientist increase confidence in the results