All elements in this series are radioactive?

    Actinide series     : All the elements in the actinides series are radiactive

Explanation:

The question is to fill in the blank which series of elements in the periodic table are radiactive.

The answer is the actnide series.

The actinide series is the elements in the same row as actinide since the same actnide (atomic number 89)  to the lawrencium (atomic number 103).

Among other elements, this series include thorium, uranium and plutonium which are very known as radiactive elements, since they are used in nuclear reactors, which use  nuclear fission reactions.

The reason for the radioactivity of these elements is the massive unstable nucleus.

A heavy nucleus means a large amount of positive charge (protons)  concentrated in a tiny region (the nucleus of the atom).

The electrostatic repulsion among those so many protons is not balanced by the strong nuclear force (from the neutrons) resulting in the unstability (radioactivity) of the nucleus.

-first use of geothermal energy occurred more than 10,000 years ago in north america by american paleo-indians

-the first industrial use of geothermal energy began near pisa, italy in late 18th century

-in 1904, italian scientist piero ginori conti invented the first geothermal electric power plant in which steam was used to generate the power

-with the above experiment, the first geothermal plant in usa started in 1922 with a capacity of 250 kilowatts

-however, in 1946 first ground-source geothermal heat pump installed at commonwealth building in portland, oregon

-during the 1960’s, pacific gas and electric began operation of first large scale geothermal power plant in san francisco, producing 11 megawatts

-in 1973, when oil crisis began many countries began looking for renewable energy sources and by 1980’s geothermal heat pumps (ghp) started gaining popularity in order to reduce heating and cooling costs

-as effect of climate change started showing results, governments of various countries joined hands to fight against it, for which kyoto protocol was signed in japan in 1997, laid out emission targets for rich countries and required that they transfer funds and technology to developing countries, 184 countries have ratified it

hope this

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.