I think there might be some confusion happening between the concept of elemental energies and the periodic elements.
The elements of things like copper, nickel, gold, silicon, etc are scientific periodic elements. Physical examples of an individual atomic structure in it's purest form. These are chemical elements. Pure substances. Though they can have some energetic/spiritual associations when in their natural states, these are more often molecules of two or more elements that have formed into a crystalline (geometrically locked) structure. For example silicone dioxide (quartz). Some don't form patterned structures and are more amorphous (many-shaped) stones, but they can still present specific energetic traits. This is the premise behind energy-working through crystals.
Books like 'the crystal bible' go into encyclopedic detail and might be a great resource if you are referring to the elements in this way. It is a new-age and spiritualistic approach to working energy, and is not at all uncommon within magical practices.
The other use of the term 'elements' refers to a philosophical/representative definition of energetic categories. Often recognized as the conceptual building-blocks of the world around us, like chemical elements, but more representative in nature. These categories are probably more similar to states or qualities of matter though, instead of literal atomic structure.
The big four being fire, water, air, earth. Each one is representative of a natural and philosophical/conceptual force. I suppose a more modern few might lump the idea of electromagnetics in with this, as it would fit thematically, but for some reason it isn't a mainstream inclusion.
Each element represents an array of natural phenomena and also reflects particular human traits. Fire is a raw expression of manifest energy as it produces light and heat. It also represents power and aggression, active change, and force of will. Water is about mystery, emotion, being cooling/an absorber of energy and a reflection to fire's heat. Earth is long lasting. Enduring, always healing and supporting. But slow moving (if at all) and firm. Typically used in reference to anything having a relation to the embodiment of the living planet. (Sometimes death, rebirth, and the underworld). And the opposite, air, is an expression of thought (without emotion). Free-flowing, loose, always changing. One moment a cacophony of motion and the next still and calm. Transient but far-reaching.
This part is a bit of personal gnosis, but I find the additional elements to be an exploration of the interactions between the main four. Clouds (or storms) would be an interaction of water and fire. Lightning would be air and fire. Wood could be earth and water (life), metal would be earth and fire, and so-on. While many things can be said to have some mixture or ratio of many elements, certain phenomena could be conceived as a balanced and equal combination of two. The result of a 'perfect mix'.
It seems logical that this understanding of the elements is centered in the very distant past. Way back then, learning and experience was predominantly observational. Oceans were unpredictable and fickle, being glass one day and tumultuous the next. Deep water could be calm on the surface but a swirling storm below. Earth is where food grows and life happens. Earth protects us in the form of shelter and walls. It heals us through herbs. Fire empowers us, gives light and warmth but must be handled with care lest it destroy. That understanding, combined with a generally animistic world concept and the notion that 'like attracts like', becomes a basis for many core processes behind magical practice, traditions, and symbolisms.
...And also influencing science and medicine even as recently as just a couple hundred years ago.