Excuse me: the atomic model closest to the real atomic structure is () a Thomson model B Rutherford model C Bohr stratification model d electron cloud model The best reason is comprehensive Each option is analyzed

Excuse me: the atomic model closest to the real atomic structure is () a Thomson model B Rutherford model C Bohr stratification model d electron cloud model The best reason is comprehensive Each option is analyzed

The answer is d
1. Thomson model is overthrown by Rutherford model;
2. The Rutherford model only separates the atom into nucleus and extranucleus electrons;
3. The Bohr model begins to consider the states of extranuclear electrons;
4. The electron cloud model, combined with quantum theory, is the closest model to the actual atomic structure

How to correctly understand the sentence "s electron cloud is spherically symmetric"?

First of all, what is an electron cloud? An electron cloud does not really exist. It is just a method used by scientists to express the distribution of electrons outside the nucleus. The density of the points is used to express the probability of the emergence of electrons at the corresponding position. It can be imagined that the probability of the emergence of electrons in any direction at the same radius outside the nucleus of the S layer is the same. What is such a distribution not spherical

Let f (x, y) have first order continuous partial derivatives, and f (x, x2) = 1, f ′ x (x, x2) = x, find f ′ y (x, x2) (X2 is the square of x)

f(x,x^2)=1
The derivation of X on both sides is as follows:
fx(x,x^2)+fy(x,x^2)2x=0
fy(x,x^2)=-fx(x,x^2)/(2x)=-1/2

The square reduction of (a + 1)

a^2+2a+1

The distance between a and B is 40 km, the speed of motorcycle is 45 km, and the speed of truck is 35 km. How long does it take for the two vehicles to travel in opposite directions? The distance between the two vehicles is 10 km

The two cars passed 10 kilometers apart
﹙40-10﹚÷﹙45+35﹚
=30÷80
=3/8
The unit writes according to the title

Let x = 3 be the solution B of the equation AX + 6 = - 4x-12 and satisfy the relation ⁃ 2B + a = 14, then the value of ⁃ a + B ⁃ can be obtained

3a+6=-4*3-12
a=-10
2B + a = 14
2B + a = 14 or 2B + a = - 14
B = 12 or B = - 2
A + B = 12-10 = 2 or a + B = - 2-10 = - 12

A and B start from a to B at the same time. A travels 50 kilometers per hour, B 40 kilometers per hour,
On the way, car a broke down and stopped for repair for 3 hours. As a result, car a arrived at place B one hour later than car B. how many kilometers is the distance between a and B?

Let the distance between AB and ab be x km
（X/50+3）—X/40=1
The solution is x = 400
So the distance between AB and ab is 400 kilometers

How to write 2x + 3x = 60 in equation and test it
There are also practices and tests of 3.6x-2.8x = 12 and 100x-x = 198

1) 2x+3x=60
5x=60
x=12
2)3.6x-2.8x=12
0.8x=12
x=1.5
3)100x-x=198
99x=198
x=2
In the test, 12, 1.5 and 2 points are brought into the corresponding equation to see if the equation is true

When will they meet if they start at the same time?

Let their meeting time be X
Then (2 + 1.5) x = 7000
X = 2000 seconds

The decimal point of a decimal is moved one place to the left, and the number obtained is 2.52 less than the original number. This decimal is______ ．

2.52 ÷ (1-110), = 2.52 ÷ 910, = 2.8; answer: the decimal is 2.8, so the answer is: 2.8