Answer: Elements in Group 2
Explanation: The periodic table was arranged by Dmitri Mendeleev specifically around similarites in their chemical behaviors. He found that as atomic number increases, at some point an element starts to react in a manner similar to a previous one. When that happened, he would place the larger element under the smaller one, and eventually noticed a periodicity in the table. Elements in a column (Groups) had similiar chemical properties. We know today that these similarities are due to the electron configuration, and that these configurations repeat themselves. He left gaps in the table when he could find an existing element with properties similar to others in that group. I big leap of faith, but it worked. Elements for those missing boxes were eventually discovered.
Answer:
Polar covalent bond
Explanation:
When the electronegativity difference between two elements A and X is 0.8, the bond AX formed will most likely be a polar covalent bond.
A polar covalent bond is one whose electronegativity difference is between 0.5 and 2.1.
In such a bond type, we have heteronuclear species with one of the species having a higher electronegativity value.
- When electronegativity difference is less than 0.5, a non-polar covalent bond forms.
- If the value is greater than 2.1, an ionic bond will form.
I believe with a simple google search that 99.9
<u>Answer:</u> The mass of chlorine needed by the plant per day is 
<u>Explanation:</u>
We are given:
Volume o water treated per day = 25,000,000 gallons
Converting this volume from gallons to liters, we use the conversion factor:
1 gallon = 3.785 L
So, 
Amount of chlorine applied for disinfection = 10 mg/L
Applying unitary method:
For 1 L of water, the amount of chlorine applied is 10 mg
So, for 
of water, the amount of chlorine applied will be 
Hence, the mass of chlorine needed by the plant per day is
