<h3>
Answer:</h3>
Al- [Ne] 3s²3p¹
As- [Ar] 4s²3d¹⁰ 4p³
Explanation:
- Electron configuration of an element shows the arrangement of electrons in the energy levels or orbitals in the atom.
- Noble-gas configuration involves use of noble gases to write the configuration of other elements.
- This is done by identifying the atomic number of the element and then identifying the noble gas that comes before that particular element on the periodic table.
- Aluminium: The atomic number of Al is 13. The noble gas before Aluminium is Neon which has 10 electrons. Therefore the remaining 3 electrons fills up the 3s and 3p sub orbitals.
- Thus, the noble-gas configuration of Al is [Ne] 3s²3p¹
2. Arsenic, Atomic number is 33
- Noble gas before Arsenic is Ar,. Argon has 17 electrons, then the remaining electrons fills up the 4s, 3d and 4p sub-orbitals.
- Thus, the noble-gas configuration of As is [Ar] 4s²3d¹⁰ 4p³
When you are asked a question like this, you can always ask yourself this question. Can I change it back after this change? For example, if you are burning wood, you cannot bring it back to wood after you burn it, therefore, it is a chemical change. However, if you boil and evaporate water, you can make the water condense again back into its liquid form. In this case, you cannot bring the tomato back to its raw state. Therefore, cooking raw tomatoes is a chemical change.
Answer: c.They have a unique set of properties that can be used as identifiers.
Explanation:
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.
Compounds can be decomposed into simpler constituents using chemical reactions.
Example: Water 
Compounds have different properties than the elements it is made up of.
Thus the most accurate description of compounds is that they have a unique set of properties that can be used as identifiers.
Answer:
204.5505 grams
2.5666 moles
Explanation:
For the first question, multiply 3.5 (# of moles) by 58.443 (g/mol for NaCl).
58.443 * 3.5
<em>I'll distribute 3.5 into 58.443.</em>
(3.5 * 50) + (3.5 * 8) + (3.5 * 0.4) + (3.5 * 0.04) + (3.5 * 0.003)
175 + 28 + 1.4 + 0.14 + 0.0105
203 + 1.4 + 0.14 + 0.0105
204.4 + 0.14 + 0.0105
204.54 + 0.0105
204.5505 grams
There are 204.5505 grams in 3.5 moles of NaCl.
For the second question, divide 150 (# of grams) by 58.443 (g/mol for NaCl). I'll convert both into fractions.
150/1 * 1000/58443
150000/58443
2.56660336 moles
2.5666 moles (rounded to 4 places to keep consistency with the first answer) are in 150 grams of NaCl.
Did u mean mass of potassium nitrate or the mass of nitrogen in potassium nitrate
