1. true or false? bases change litmus paper to blue.
2. true or false? ammonia is an acid.
3. true or false? properties of acids include being corrosive and having a sour taste.
4. true or false? sulfuric acid is known as a strong acid.
5. true or false? base solutions have a ph below 7.
6. true or false? the chemical formula for sulfuric acid is h2so4.
7. true or false? lemons contain citric acid.
8. true or false? an alkali is an acid.
9. true or false? an anion is an ion with more electrons than protons, giving it a negative charge.
10. true or false? neutral solutions have a ph of 0.
11. true or false? acids change litmus paper to red.
12. true or false? the word acid comes from the latin word acidus (meaning sour).
13. true or false? the chemical formula for sodium hydroxide is nah.
14. true or false? a cation is an ion with more protons than electrons, giving it a positive charge.
15. true or false? acetic acid gives vinegar a sour taste and strong smell.
16. true or false? acid solutions have a ph above 7.
17. true or false? formic acid is found in bee venom.
18. true or false? sodium hydroxide is known as a weak base.
19. true or false? dna is an abbreviation for deoxyribonucleic acid.
20. true or false? potassium hydroxide contains potassium, oxygen and helium.

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.

the answer to this question is 3.