Draw electron dot diagrams for the following elements and ions. a. ca b. k+ c. o2- d. o

Here's what I get  

Explanation:

See the image below.

Ca is in Group 2. It has two valence electrons.

K is in Group 1. It has one valence electron. The + sign shows that it has lost the electron, so there are no dots around the symbol.

O is in Group 16. It has six valence electrons. The 2- shows that it has gained two electrons, for a total of eight, so there are eight dots around the symbol,

The electron dot diagram for O shows six dots for its valence electrons.

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.