The first published classification of the periodic table is by Dmitri Mendeleev who arranged it by atomic mass, but it was later rearranged by Henry Moseley by atomic number. This forms the basis of the modern periodic table. Various chemistry concepts related to the periodic table such as groups, periods, valence electrons, and names of certain elements are also discussed.
The first published classification of elements which forms the basis of our periodic table today was by Dmitri Mendeleev. Mendeleev initially arranged the elements by their atomic mass, and he noticed that the properties of elements repeated periodically when arranged in this order. However, later on, Henry Moseley suggested that the periodic table be arranged by atomic number (the number of protons in an atom's nucleus), which is how the modern periodic table is ordered.
"The properties of the elements repeat periodically" defines the Periodic Law. A 'period' in the periodic table is a horizontal row and there are 7 periods. A 'group' or 'family' in the periodic table is a vertical column and there are 18 groups.
Magnesium has 2 valence electrons, Phosphorous has 5, Fluorine has 7, and Neon has 8. The elements with atomic numbers 13, 92, 5, and 25 are Aluminum (Al), Uranium (U), Boron (B), and Manganese (Mn) respectively.
Beryllium (Be) belongs to period 2 and group 2, Iron (Fe) is in period 4 and group 8, and Lead (Pb) is in period 6 and group 14. The two pairs of elements that belong to the same period are Na and Cl, and Na and Ne. The pairs that belong to the same group are H and He, and Ga and Ge.
The transition elements are in groups 3-12. The group 1/IA elements are called Alkali metals, the group 2/IIA elements are called Alkaline earth metals, the group 17/VIIA elements are called Halogens, and the group 18/VIIIA elements are called Noble gases. The alkali metal that belongs to the sixth period is Cesium, the halogen that belongs to the fourth period is Bromine, the element in the fifth period and the eleventh group is Silver. The heaviest noble gas is Radon and the heaviest alkaline earth metal is Radium. Strontium is chemically more similar to Calcium, as they are in the same group and have the same number of valence electrons. The three lightest noble gases are Helium, Neon, and Argon, and the alkali metals are Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium.
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It is often greater than it was before the collision.
It is always the same as it was before the collision.
It is often the same as it was before the collision.
Answer:
It is always the same as it was before the collision.
Answer:
The answer is C on Edge
Explanation:
You do 50 Joule work when you pick up your sled, lifting it 0.5meter upward.
You do no work to carry the sled to your home.
Work in physics is the energy that is transferred to or from an item when a force is applied along a displacement. For a constant force acting in the same direction as the motion, the work is simply equal to the product of the force's magnitude and the distance travelled.
When a force is applied, it is said to have a component that moves the point of application, or it is said to have positive work.
Hence, lifting it 0.5meter upward, you have to work = weight of the sled × distance × cos 0°
= 100 N × 0.5 meter × 1
= 50 Joule.
To carry the sled to your home, you have to work = weight of the sled × distance × cos 90°
= 100 N × 800 m × 0
= 0.
Learn more about work here:
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Answer:
v = R w
With this expression we see that for each point at different radius the tangential velocity is different
Explanation:
They indicate that the angular velocity is constant, that is
w = dθ / dt
Where θ is the radius swept angle and t the time taken.
The tangential velocity is linear or
v = dx / dt
Where x is the distance traveled in time (t)
In the definition of radians
θ = s / R
Where s is the arc traveled and R the radius vector from the pivot point, if the angle is small the arc (s) and the length (x) are almost equal
θ = x / R
We substitute in the speed equation
v = d (θ R) / dt
The radius is a constant for each point
v = R dθ / dt
v = R w
With this expression we see that for each point at different radius the tangential velocity is different
B. Vibrating molecules
C. Radio sets
D. Vibrating charged particles
E. TV antennas
Answer:
(0.25) * (10) = 2.5 Newtons
Explanation: