<u>Answer:</u> Group 1 ions are known as cations and Group 17 ions are known as anions.
<u>Explanation:</u>
Ions are formed when an atom looses or gains electrons.
If an atom gains electrons, it leads to the formation of negative ions known as anions. <u>For Example:</u> Fluorine is a Group 17 element which gains 1 electron to form 
ions.
If an atom looses electrons, it leads to the formation of positive ions known as cations. <u>For Example:</u> Sodium is a Group 1 element which looses 1 electron to form 
ions.
Hence, group 1 ions are known as cations and Group 17 ions are known as anions.
They are nitrogen, oxygen, hydrogen
<h3>
Answer:</h3>
1.25 moles (R.T.P.) or 1.34 moles (S.T.P.)
<h3>
Explanation:</h3>
- 1 mole of a gas occupies a volume of 24 liters at room temperature and pressure (R.T.P.)
- On the other hand, 1 mole of a gas will occupy 22.4 Liters at standard temperature and pressure (S.T.P.)
Therefore, at R.T.P.
30.0 Liters will be equivalent to;
= 30.0 L ÷ 24 L
= 1.25 moles
At S.T.P
30.0 Liters will be equivalent to;
= 30.0 L ÷ 22.4 L
= 1.34 moles
Thus, 30.0 L of helium gas are equivalent to 1.25 moles of He at R.T.P. and 1.34 moles at S.T.P.
Electron transitions from higher to lower energy levels cause emission of energy in the form of electromagnetic waves, each with their own specific wavelength. Because the energy levels of elements are quantized, each transition has a specific energy difference. The collection of these transitions makes up the emission spectrum and each spectrum is unique to a specific element, allowing identification.
