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otez555 [7]
3 years ago
7

How many neutrons does element X have if its atomic number is 43 and its mass number is 164?

Physics
2 answers:
Brilliant_brown [7]3 years ago
7 0
The atomic number is 43. This means it is Technetium. If its mass number is 164, then the number of neutrons is: 164 - 43 = 121. It has 121 neutrons.
Drupady [299]3 years ago
6 0
Hello, 
The mass number is protons+neutrons=mass number. In this case, we have protons+nuetron=164.The atomic number is simply the number of protons so we have 43+neutrons=164. Subtracting 43 from both sides we get nuetrons=121. Hope this helps!
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a cement block accidentally falls from rest from the ledge of a 80.6-m-high building. When the block is 10.8 m above the ground,
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Answer:

0.229 seconds

Explanation:

Given:

y₀ = 80.6 m

v₀ = 0 m/s

a = -9.8 m/s²

We need to find the difference in times when y = 10.8 m and y = 2.10 m.

When y = 10.8 m:

y = y₀ + v₀ t + ½ at²

10.8 = 80.6 + (0) t + ½ (-9.8) t²

10.8 = 80.6 − 4.9 t²

4.9 t² = 69.8

t = 3.774

When y = 2.10 m:

y = y₀ + v₀ t + ½ at²

2.10 = 80.6 + (0) t + ½ (-9.8) t²

2.10 = 80.6 − 4.9 t²

4.9 t² = 78.5

t = 4.003

The difference is:

4.003 − 3.774 = 0.229

The man has 0.229 seconds to get out of the way.

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4 years ago
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Answer:

It would not be possible the cohesion among water molecules by the polar covalent bonding.

Well, to understand this in a better way, let's begin by explaining that water is special due to its properties, which makes this fluid useful for many purposes and for the existence of life.

In this sense, one of the main properties of water is cohesion (molecular cohesion), which is the attraction of molecules to others of the same type. So, water molecule (H_{2}O) has 2 hydrogen atoms attached to 1 oxygen atom and can  stick to itself through hydrogen bonds.

How is this possible?

By the polar covalent bonding, a process in which electrons are shared unequally between atoms, due to the unequal distribution of electrons between atoms of different elements. In other words: slightly positive and slightly negative charges appear in different parts of the molecule.  

Now, it can be said that a water molecule has a negative side (oxygen) and a positive side (hydrogen).  This is how the oxygen atom tends to monopolize more electrons and keeps them away from hydrogen. Thanks to this polarity, water molecules can stick together.

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