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Bad White [126]
3 years ago
7

One radioactive isotope of calcium has an atomic mass of 47,how many neutrons are in the calcium -47 nucleus

Chemistry
1 answer:
jekas [21]3 years ago
6 0

Answer: 27 neutrons

Explanation:

Recall that the number of protons in the nucleus of an atom = Atomic number.

Hence, Calcium with mass number 47 and atomic number 20 will have 20 protons

Therefore, since Mass number = number of protons + neutrons

47 = 20 + neutrons

Neutrons = 47 - 20 = 27

Thus, there are 27 neutrons in radioactive calcium nucleus.

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Molecular and empirical formulas
shepuryov [24]

Answer:

See below

Explanation:

Molecular formula  ( just write down all of the elements )   C 4 H4 O4

Empiracle formual    CHO

"Molecular formulas tell you how many atoms of each element are in a compound, and empirical formulas tell you the simplest or most reduced ratio of elements in a compound"

7 0
2 years ago
The quantum numbers for the last electron placed in three elements are listed below. Which of these is(are) NOT correct? Er (4 3
UNO [17]

Answer:

The three elements Erbium, Thallium and Osmium have incorrect quantum numbers for the last electron placed.

Explanation:

The 4 quantum numbers are (<em>n,l,ml,ms</em>):

  • <em>n</em> (Principal quantum number): it is the <u>number of the shell (level)</u> where the electron is placed.
  • <em>l </em>(Angular momentum quantum number or Secondary): it represents the <u>sublevel where the electron is</u> placed. There are 4 subleves: s, p d and f so secondary quantum number can take the number 0 (s), 1 (p), 2 (d) or 3 (f) depending on which sublevel the electron is placed.
  • <em>ml</em> (Magnetic quantum number):  it represents the <u>spatial orientation</u> of the electron <u>in respect of the sublevel the electron</u> is placed. For example: if the electron occupies the <em>s sublevel</em> the magnetic number will be <em>0</em>, if the electron occupies the <em>p sublevel</em> the magnetic number could be <em>-1,0,1</em>, if the electron occupies the <em>d sublevel</em> the magnetic number could be <em>-2,-1,0,1,2</em> and if the electron occupies the <em>f sublevel</em> the magnetic number could be <em>-3,-2,-1,0,1,2,3</em>. You can see this in the attachment related to the correct sublevel for the example.
  • <em>ms</em> (Spin quantum number): this number represents the possible rotation of the electron so it could be 1/2 (which is represented by an up arrow) or -1/2 (represented by an down arrow).

Let's analyze the last electron of each element. You can see the attachment for better understanding. The last electron it is represented with orange color.

- Erbium:

This element has 68 electrons so following the Moeller's Diagram to fill the the electronic configuration, we found that the last electron of Erbium it is in the <u>4th level </u>(shell), in the <u>f sublevel</u>. As Erbium has 12 electrons in the f sublevel, it is necessary to follow the Hund's rule (electrons must be placed singly in every sublevel before place a parallel electron) to placed correctly all of them. Finally, the last electron of Erbium stays in the middle of the sublevel and it is represented by a down arrow so the correct quantum numbers in the Erbium element are (4,3,1,-1/2).

- Thallium:

This element has 81 electrons and following the Moeller's Diagram, we found that it last electron it is in the <u>6th level</u>, in the <u>p sublevel</u>. As Thallium has 1 electron in the p sublevel, it is placed singly in the sublevel. So the last electron of Thallium it is represented by an up arrow so the correct quantum numbers in the Thallium element are (6,1,-1,1/2).

- Osmium:

Osmium has 76 electrons and following the steps  that we did with we the other elements, we noticed that its last electron it is in the <u>5th level</u>, in the <u>d sublevel</u>. Following the Hund's rule the last electron of Osmium has a magnetic quantum number of -2 and its spin quantum number is -1/2, so the quantum numbers in the Osmium element are (5,2,-2,-1/2).

<u>Note:</u>

- Remember that the <em>s sublevel</em> has place for 2 electrons, the <u>p sublevel</u> has place for 6 electrons, the <u>d sublevel</u> has place for 10 electrons and the<em> f sublevel</em> has place for 14 electrons.

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Alekssandra [29.7K]

Answer: first one

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Name the 2 isomers of c7h16 that contain 2 methyl branches, each branch on a different carbon of the parent chain.
kupik [55]
There can be a lot of meanings for isomers. In this case, we are showing the structural isomers of C₇H₁₆. Based on the chemical formula, CₓH₂ₓ₊₂ it is an alkane. They only differ in the positions of methane branches in the parent carbon chain. Basing on the attached picture, the parent carbon chain is pentane for both isomers. But the methyl branches are on the 2nd & 4th, and 2nd & 3rd carbon for 2,4 - dimethylpentane and 2,3 - dimethylpentane, respectively.

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3 years ago
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