Answer:
Mendeléyev designed his table around the same time as a German chemist named Julius Lothar Meyer, who published it a year later. However, finally Mendeléyev's order was imposed. Do you know what his great success was? Help plis.
Mendeleev predicted the existence and properties of unknown elements that he called eka-aluminum, eka-boron, and eka-silicon, his table is based on atomic weight.
Explanation:
Gallium, scandium, and germanium were later discovered to coincide with his predictions. In addition to the fact that Mendeleev's table was published before Meyers, his work was more extensive, predicting the existence of other elements not known at the time.
The representative elements are elements where the s and p orbitals are filling. The transition elements are elements where the d orbitals (groups 3–11 on the periodic table) are filling, and the inner transition metals are the elements where the f orbitals are filling.
The pH meter measure the concentration of the hydrogen(+) ion, and the concentration of Hydroxide(-). Hydrogen is acidic, Hydroxide is basic.
The answer is D.
Answer:
Therefore it will take 7.66 hours for 80% of the lead decay.
Explanation:
The differential equation for decay is
Integrating both sides
ln A= kt+c₁
[
]
The initial condition is A(0)= A₀,
.........(1)
Given that the 
has half life of 3.3 hours.
For half life 
putting this in equation (1)
[taking ln both sides, 
]
⇒k= - 0.21
Now A₀= 1 gram, 80%=0.8
and A= (1-0.8)A₀ = (0.2×1) gram = 0.2 gram
Now putting the value of k,A and A₀in the equation (1)
⇒ t≈7.66
Therefore it will take 7.66 hours for 80% of the lead decay.
