atoms of the element lead (Pb) have four valence electrons. Find lead on the periodic table to answer the following question. Which elements also have only four valence electrons?

In which situation has the independent variable for the experiment been changed? check all that apply. changed from counting the number of duckweed at day 0 and day 14 to counting them every day changed from testing duckweed growth in beakers to testing duckweed growth in large outdoor tanks changed from testing the effect of ph on duckweed growth to testing the effect of light levels on duckweed growth changed from testing the effect of acid ph on duckweed growth to testing the effect of basic ph on duckweed growth

The combining of light nuclei is called blank. blank as in not actually blank. you know what im tryin to say.

When using the scientist method, which step comes last?