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3 years ago

14

An atom has the following electron configuration . 1s^ 2 2s^ 2 2p^ 6 3s^ 2 3p^ 6 4s^ 2 How many valence electrons does this atom

have ?
2
3
5
11

1 answer:

stepan [7]3 years ago

5 0

It’s 2 because it’s the number of row it is in; the element is calcium in row 2

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A bus travels 20km in 30minutes what is the average speed of the bus?

Vera_Pavlovna [14]

Answer:

40km/hr

Explanation:

Speed = Distance ÷ Time and since they both have different units we have to change one of them. Therefore if we change 30 minutes to half an hour we say 20km ÷ ¹/2

7 0

3 years ago

To determine the age of fairly recent fossils and organic artifacts, it is possible to analyze the amounts of the isotopes 14C a

dolphi86 [110]

Answer: The net change in the atoms is the conversion of a neutron to a proton, turning Carbon (6 protons) into Nitrogen (7 protons).

Explanation:

Carbon-14, generated from the atmosphere, has 6 protons and 8 neutrons. That's where the 14 comes from, called the mass number, is the sum of protons and neutrons (6+8=14).

Carbon-14 is radioactive and decays by beta decay. That means one of its neutrons spontaneously turns into a proton, an electron, and a neutrino, according to:

$^{14} C \rightarrow\ ^{14} N\ +\ e^- +\ neutrino$

After that, the atom has 7 protons and 7 neutrons, maintaining its mass number but changing its atomic number from 6 to 7, turning into Nitrogen.

3 0

3 years ago

What nuclide undergoes fission to form molybdenum-103, atomic number 42, tin-131, atomic number 50, and two neutrons?

FrozenT [24]

Answer:

The correct answer is Pu, 234.

Explanation:

In the given case, let us consider the reactant as X. Now the mass number (balanced) on both the sides will be,

Mass of X = Mass of Molybdenum + Mass of Tin + Mass of neutrons

M = 1 * 103 + 1 * 131 + 2 * 0

M = 234

Now the atomic number (balanced) on both the sides,

Atomic number of X = Atomic number of Molybdenum + Atomic number of Tin + Atomic number of neutrons

A = 1*42 + 1*50 + 2*1

A = 94

The atomic number 94 is for the element Plutonium, whose symbol is Pu. Thus, the reactant is 234-Pu.

6 0

3 years ago

Given the two reactions PbCl2(aq)⇌Pb2+(aq)+2Cl−(aq), K3 = 1.89×10−10, and AgCl(aq)⇌Ag+(aq)+Cl−(aq), K4 = 1.25×10−4, what is the

Sergio [31]

Answer:

$1.2\times 10^{-2}$

Explanation:

The given reactions are:

PbCl2(aq)⇌Pb2+(aq)+2Cl−(aq) $K_3 = 1.89\times 10^{-10}$

AgCl(aq)⇌Ag+(aq)+Cl−(aq) $K_4 = 1.25\times 10^{-4}$

Required reaction is:

PbCl2(aq)+2Ag+(aq)⇌2AgCl(aq)+Pb2+(aq)

$K_f = \frac{K_3}{K_4^2}\\=\frac{1.89\times 10^{-10}}{1.25\times 10^{-4}}^2\\=1.2\times 10^{-2}$

4 0

3 years ago

If 585.24 Joules of heat are added to 53.2 grams of water at 24.15oC, what will the new temp. be?

spayn [35]

E = mct
Energy = (mass) x (specific heat capacity of water) x (change in temp)

585.24 = 53.2 x 4.2 x (X-24.15)

585.24 divided by 53.2 divided by 4.2 = X - 24.15

2.62 = X - 24.15

X= 26.77degrees C

(Specific heat capacity for water is 4.2 but is different for other liquids)

3 0

4 years ago