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2 years ago

Mendeleev arranged the known chemical elements in a table according to increasing

Physics

2 answers:

sladkih [1.3K]2 years ago

8 0

1- mass 2. 3 3. Li2O 4. Of the strong attraction..................

wlad13 [49]2 years ago

6 0

<h3>1. <u>Answer</u>; </h3>

Mass

Mendeleev arranged the known chemical elements in a table according to increasing <u>mass</u>.

<h3><u>Explanation</u>; </h3>

<em><u>Mendeleev arranged the elements in rows in order of increasing mass so that elements with similar properties were in the same column. He provided an organizing principle that worked for all off the known elements. </u></em>
The close match between Mendeleev’s predictions and the actual properties of new elements showed how useful his periodic table could be. He also left spaces for undiscovered elements in order to place elements with similar properties in the same column.
Mendeleev's periodic table was useful because it enabled scientists to predict properties of unknown elements.

<h3>2. <u>Answer; </u></h3>

Atomic mass unit.

One twelfth the mass of a carbon-12 atom is used to define an<em><u> atomic mass unit </u></em>

<h3><u>Explanation</u>; </h3>

<em><u>An atomic mass unit (AMU) refers to precisely 1/12 the mass of an atom of carbon-12.</u></em> The carbon-12 atom has six protons and six neutrons in its nucleus. One AMU is the average of the proton rest mass and the neutron rest mass.

<em><u>The mass of an atom in atomic mass unit is approximately equal to the sum of the number of protons and neutrons in the nucleus. </u></em>
The atomic mass unit expresses the relative masses of various isotopes of elements.

<h3>3. <u>Answer</u>; </h3>

Five electrons

A member of the boron family has three valence electrons, while a member of the nitrogen family has<u> five electrons</u>.

<h3><u>Explanation</u>; </h3>

The number of valence electrons is the number of electrons in the outermost energy level of an atom.
<em><u>Nitrogen family includes, non-metals, metalloids, and metals. The atoms of these elements in the nitrogen family have a 5 valence electrons. </u></em>The family include elements, phosphorus, bismuth, arsenic and antimony. They form bonds through sharing of electrons.

<h3>4. <u>Answer; </u></h3>

Li2O

<h3><u>Explanation; </u></h3>

<em><u>Ionic compounds are compounds that are made up of ions. They are formed as a result of transfer of electrons from one atom to another.</u></em> One atom loses electrons while the other atom gains electrons, resulting to formation of negatively charged ion (anion) and positively charged ion (cation) which join via ionic bond to form an ionic compound.

<em><u>Lithium oxide is an example of ionic compound formed from lithium and oxygen atoms. Lithium has a valency of one while oxygen has a valency of two, therefore, the chemical formula of lithium oxide will be Li2O. </u></em>

<h3>5. <u>Answer</u>; </h3>

Of the strong attractions between polar water molecules

Water has a higher boiling point than expected because <u>of the strong attractions between polar molecules. </u>

<h3><u>Explanation; </u></h3>

Water has a high boiling point because of intermolecular forces of attraction called hydrogen bonds. <u>Hydrogen bonding</u> is a form of dipole-dipole interaction, where a molecule that is partially positive is attracted to another molecule that is partially negative.

<em><u>Hydrogen bond being a powerful intermolecular force, it makes water to have a high boiling point, because they require more energy to break the bond.</u></em>

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The _____ theory is the most accepted theory regarding the origin of the solar system. It suggests that our star, the Sun, was f

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The Nebular Hypothesis is the most accepted explanation of the origin of our solar system. It states that the Sun was formed by a massive cloud of dust and gas light-years across, and it was bigger than the actual sun itself. Most of the mass in the center formed the sun, and the rest expanded outward.

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3 years ago

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A particle leaves the origin with an initial velocity v → = (3.00iˆ) m/s and a constant acceleration a → = (−1.00iˆ − 0.500jˆ) m

tatiyna

Answer:

the position vector (x,y) will be (1.5 m,-2.25 m) and the velocity vector (vx,vy) will be ( 0 m/s , -1.5 m/s) when x reaches its maximum x coordinate

Explanation:

Since the velocity is related with the acceleration and coordinates through

vx²=v₀x²+2*ax*x

where

vx = velocity in the x direction

v₀x = initial velocity in the x direction = 3 m/s

ax = acceleration in the x direction = −1.00 m/s²

x= coordinates in the x-axis

when x reaches its maximum coordinate , then vx=0

thus

vx²=v₀x²+2*ax*x

0 = (3 m/s)² + 2* (−1.00 m/s²)*x

x= 1.5 m

also for the time t

vx = v₀x + ax*t → t= (vx-v₀x)/ax = (0- 3 m/s)/ (−1.00 m/s²) = 3 seconds

for the y coordinates

y = y₀+v₀y*t + 1/2 ay*t²

where

v₀y = initial velocity in the y direction = 0 m/s

ay = acceleration in the x direction = −0.5 m/s²

y= coordinates in the y-axis

y₀= initial coordinate in the y-axis =0

then since y₀=0 and v₀y=0

y = 1/2*ay*t²

y = 1/2*ay*t² = 1/2*(−0.5 m/s²)*(3 s)² = -2.25 m

and

vy=v₀y+ ay*t= 0+(−0.5 m/s²)*(3 s)= (-1.5 m/s)

therefore the position vector (x,y) will be (1.5 m,-2.25 m)

and the velocity vector (vx,vy) will be ( 0 m/s , -1.5 m/s)

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2 years ago

Which of the following takes place during a double displacement reaction?

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Double displacement: parts of compounds switch places to form two new compounds

FYI
decomposition: a complex substance breaks down into two or more simple substances

Single displacement: a single substance replaces another substance in a compound

<span>Synthesis: two simple substances combine to form a new complex substance</span>

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3 years ago

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While entering a freeway, a car accelerates from rest at a rate of 2.40 m/s2 for 12.0 s. (a) Draw a sketch of the situation. (b)

ArbitrLikvidat [17]

Answer:

a) See attached picture, b) We know the initial velocity = 0, initial position=0, time=12.0s, acceleration= $2.40m/s^{2}$ , c) the car travels 172.8m in those 12 seconds, d) The car's final velocity is 28.8m/s

Explanation:

a) In order to draw a sketch of the situation, I must include the data I know, the data I would like to know and a drawing of the car including the direction of the movement and its acceleration, just like in the attached picture.

b) From the information given by the problem I know:

initial velocity =0

acceleration = $2.40m/s^{2}$

time = 12.0 s

initial position = 0

unknown:

displacement.

in order to choose the appropriate equation, I must take the knowns and the unknown and look for a formula I can use to solve for the unknown. I know the initial velocity, initial position, time, acceleration and I want to find out the displacement. The formula that contains all this data is the following:

$x=x_{0}+V_{x0}t+\frac{1}{2}a_{x}t^{2}$

Once I got the equation I need to find the displacement, I can plug the known values in, like this:

$x=0+0(12s)+\frac{1}{2}(2.40\frac{m}{s^{2}} )(12s)^{2}$

after cancelling the pertinent units, I get that my answer will be given in meters. So I get:

$x=\frac{1}{2} (2.40\frac{m}{s^{2}} )(12s)^{2}$

which solves to:

$x=172.8m$

So the displacement of the car in 12 seconds is 172.8m, which makes sense taking into account that it will be accelerating for 12 seconds and each second its velocity will increase by 2.4m/s.

d) So, like the previous part of the problem, I know the initial position of the car, the time it travels, the initial velocity and its acceleration. Now I also know what its final position is, so we have more than enough information to find this answer out.

I need to find the final velocity, so I need to use an equation that will use some or all of the known data and the unknown. In order to solve this problem, I can use the following equation:

$a=\frac{V_{f}-V_{0} }{t}$

Next, since I need to find the final velocity, I can solve the equation just for that, I can start by multiplying both sides by t so I get:

$at=V_{f}-V_{0}$

and finally I can add $V_{0}$ to both sides so I get:

$V_{f}=at+V_{0}$

and now I can proceed and substitute the known values:

$V_{f}=at+V_{0}$

$V_{f}=(2.40\frac{m}{s^{2}}} (12s)+0$

which solves to:

$V_{f}=28.8m/s$

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3 years ago

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What are the units, if any, of the particle in a box wavefunction. What does this mean?

SIZIF [17.4K]

Answer:

$[\psi]= [Length^{-3/2}]$
This means that the integral of the square modulus over the space is dimensionless.

Explanation:

We know that the square modulus of the wavefunction integrated over a volume gives us the probability of finding the particle in that volume. So the result of the integral

$\int\limits^{x_f}_{x_0} \int\limits^{yf}_{y_0} \int\limits^{z_f}_{z_0} |\psi|^2 \, dz \, dy \, dx$

must be dimensionless, as represents a probability.

As the differentials has units of length

$[dx]=[dy]=[dz]=[Length]$

for the integral to be dimensionless, the units of the square modulus of the wavefunction has to be:

$[\psi]^2 = [Length^{-3}]$

taking the square root this gives us :

$[\psi] = [Length^{-3/2}]$

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3 years ago